CVE-2026-63984

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With n=127 (cmpri=15, cmpre=15, pad=0, hdrlen=16):\n\n (128 * 16) >> 3 = 256, truncated to 0 as __u8\n\nThe caller in ipv6_rpl_srh_rcv() then places the compressed header\nat buf + ((ohdr->hdrlen + 1) << 3). With hdrlen=0 this is buf + 8,\nbut the decompressed region occupies buf[0..2055] (8-byte header\nplus 128 full addresses). The compressed header overlaps the\ndecompressed data, and ipv6_rpl_srh_compress() writes into this\noverlap, corrupting the routing header of the forwarded packet.\n\nThe existing guard at exthdrs.c:546 checks (n + 1) > 255, which\nprevents n+1 from overflowing unsigned char (the segments_left\nfield), but does not prevent the computed hdrlen from overflowing\n__u8. n=127 passes because 128 <= 255, yet hdrlen=256 does not\nfit.\n\nTighten the bound to (n + 1) > 127. This caps n at 126, giving\nhdrlen = (127 * 16) >> 3 = 254, which fits in __u8. The compressed\nheader then lands at buf + ((254 + 1) << 3) = buf + 2040, exactly\npast the decompressed region (buf[0..2039]). No overlap. 127\nsegments is well beyond any realistic RPL deployment."}], "metrics": [{"cvssV3_1": {"version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H", "baseScore": 9.8, "baseSeverity": "CRITICAL"}, "scenarios": [{"lang": "en", "value": "AV:N - The vulnerable code runs in the IPv6 routing-header receive handler on incoming packets; a remote attacker can deliver a crafted RFC 6554 type-3 RPL SRH to an RPL-enabled router or gateway over the network.\nAC:L - Triggering requires only a deterministically crafted SRH (e.g., n=127, CmprI=15, CmprE=15, pad=0, hdrlen=16, segments_left>0); all of these fields are fully attacker-controlled once the target has rpl_seg_enabled.\nPR:N - No authentication or local privileges are needed to send the malicious IPv6 packet; rpl_seg_enabled is a victim-side deployment setting on RPL routers/gateways (IoT/industrial mesh), not an attacker privilege requirement.\nUI:N - Exploitation is achieved solely by sending a malformed network packet and does not require any action from a victim user.\nS:U - Impact is confined to kernel memory corruption and packet forwarding within the same kernel security boundary; this is not a VM escape, sandbox escape, or cross-authority boundary violation.\nC:H - The hdrlen truncation causes overlapping read/write of the same kmalloc buffer during decompress/recompress, constituting kernel heap memory corruption that can be leveraged for information disclosure primitives.\nI:H - ipv6_rpl_srh_compress() performs out-of-bounds writes into the overlapping decompressed region, corrupting routing-header data that is then memcpy'd into the forwarded skb, enabling memory corruption exploitable for control-flow or data modification.\nA:H - Kernel heap corruption during SRH processing can cause kernel oops, panics, or repeated crashes when processing or forwarding the corrupted packet, consistent with high availability impact for memory-corruption bugs."}]}], "affected": [{"product": 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{"version": "6.1.176", "lessThanOrEqual": "6.1.*", "status": "unaffected", "versionType": "semver"}, {"version": "6.6.143", "lessThanOrEqual": "6.6.*", "status": "unaffected", "versionType": "semver"}, {"version": "6.12.93", "lessThanOrEqual": "6.12.*", "status": "unaffected", "versionType": "semver"}, {"version": "6.18.35", "lessThanOrEqual": "6.18.*", "status": "unaffected", "versionType": "semver"}, {"version": "7.0.12", "lessThanOrEqual": "7.0.*", "status": "unaffected", "versionType": "semver"}, {"version": "7.1", "lessThanOrEqual": "*", "status": "unaffected", "versionType": "original_commit_for_fix"}]}], "cpeApplicability": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.7", "versionEndExcluding": "5.10.259"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.7", "versionEndExcluding": "5.15.210"}, 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"https://git.kernel.org/stable/c/fd238c51b0fa5390cceca9f1ac5a9ffda8063eed"}, {"url": "https://git.kernel.org/stable/c/3618b34942b76471d044369bfd30d58c39068bf1"}, {"url": "https://git.kernel.org/stable/c/97e06791368c01f0ad2a4b3269c2abe19485ca32"}, {"url": "https://git.kernel.org/stable/c/de02fc049352af5a9595f015511222d0a85c326b"}, {"url": "https://git.kernel.org/stable/c/6fe1cb312038516cb4d9fa089d700af7059f1a64"}, {"url": "https://git.kernel.org/stable/c/c0487a9c1e116cf349e2d1f302d9019670460858"}, {"url": "https://git.kernel.org/stable/c/9d5e7a46a9f6d8f503b41bfefef70659845f1679"}], "title": "ipv6: rpl: fix hdrlen overflow in ipv6_rpl_srh_decompress()", "x_generator": {"engine": "bippy-1.2.0"}}, "adp": [{"metrics": [{"other": {"type": "ssvc", "content": {"id": "CVE-2026-63984", "role": "CISA Coordinator", "options": [{"Exploitation": "none"}, {"Automatable": "yes"}, {"Technical Impact": "total"}], "version": "2.0.3", "timestamp": "2026-10-16T15:34:39.184194Z"}}}], "problemTypes": [{"descriptions": [{"lang": "en", "type": "CWE", "cweId": "CWE-190", "description": "CWE-190 Integer Overflow or Wraparound"}]}], "title": "CISA ADP Vulnrichment", "providerMetadata": {"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "shortName": "CISA-ADP", "dateUpdated": "2026-10-19T20:18:00.765Z"}}]}}

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Triggering requires only a deterministically crafted SRH (e.g., n=127, CmprI=15, CmprE=15, pad=0, hdrlen=16, segments_left>0); all of these fields are fully attacker-controlled once the target has rpl_seg_enabled.\nPR:N - No authentication or local privileges are needed to send the malicious IPv6 packet; rpl_seg_enabled is a victim-side deployment setting on RPL routers/gateways (IoT/industrial mesh), not an attacker privilege requirement.\nUI:N - Exploitation is achieved solely by sending a malformed network packet and does not require any action from a victim user.\nS:U - Impact is confined to kernel memory corruption and packet forwarding within the same kernel security boundary; this is not a VM escape, sandbox escape, or cross-authority boundary violation.\nC:H - The hdrlen truncation causes overlapping read/write of the same kmalloc buffer during decompress/recompress, constituting kernel heap memory corruption that can be leveraged for information disclosure primitives.\nI:H - ipv6_rpl_srh_compress() performs out-of-bounds writes into the overlapping decompressed region, corrupting routing-header data that is then memcpy'd into the forwarded skb, enabling memory corruption exploitable for control-flow or data modification.\nA:H - Kernel heap corruption during SRH processing can cause kernel oops, panics, or repeated crashes when processing or forwarding the corrupted packet, consistent with high availability impact for memory-corruption bugs."}]}], "affected": [{"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "vendor": "Linux", "product": "Linux", "versions": [{"status": "affected", "version": "8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3", "lessThan": "75b3680047bf09af8e7e471a7a6ddf2ce5847f56", "versionType": "git"}, {"status": "affected", "version": "8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3", "lessThan": "fd238c51b0fa5390cceca9f1ac5a9ffda8063eed", "versionType": "git"}, {"status": "affected", "version": "8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3", "lessThan": "3618b34942b76471d044369bfd30d58c39068bf1", "versionType": "git"}, {"status": "affected", "version": "8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3", "lessThan": "97e06791368c01f0ad2a4b3269c2abe19485ca32", "versionType": "git"}, {"status": "affected", "version": "8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3", "lessThan": "de02fc049352af5a9595f015511222d0a85c326b", "versionType": "git"}, {"status": "affected", "version": "8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3", "lessThan": "6fe1cb312038516cb4d9fa089d700af7059f1a64", "versionType": "git"}, {"status": "affected", "version": "8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3", "lessThan": "c0487a9c1e116cf349e2d1f302d9019670460858", "versionType": "git"}, {"status": "affected", "version": "8610c7c6e3bd647ff98d21c8bc0580e77bc2f8b3", "lessThan": "9d5e7a46a9f6d8f503b41bfefef70659845f1679", "versionType": "git"}], "programFiles": ["net/ipv6/exthdrs.c"], "defaultStatus": "unaffected"}, {"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "vendor": "Linux", "product": "Linux", "versions": [{"status": "affected", "version": "5.7"}, {"status": "unaffected", "version": "0", "lessThan": "5.7", "versionType": "semver"}, {"status": "unaffected", "version": "5.10.259", "versionType": "semver", "lessThanOrEqual": "5.10.*"}, {"status": "unaffected", "version": "5.15.210", "versionType": "semver", "lessThanOrEqual": "5.15.*"}, {"status": "unaffected", "version": "6.1.176", "versionType": "semver", "lessThanOrEqual": "6.1.*"}, {"status": "unaffected", "version": "6.6.143", "versionType": "semver", "lessThanOrEqual": "6.6.*"}, {"status": "unaffected", "version": "6.12.93", "versionType": "semver", "lessThanOrEqual": "6.12.*"}, {"status": "unaffected", "version": "6.18.35", "versionType": "semver", "lessThanOrEqual": "6.18.*"}, {"status": "unaffected", "version": "7.0.12", "versionType": "semver", "lessThanOrEqual": "7.0.*"}, {"status": "unaffected", "version": "7.1", "versionType": "original_commit_for_fix", "lessThanOrEqual": "*"}], "programFiles": ["net/ipv6/exthdrs.c"], "defaultStatus": "affected"}], "references": [{"url": "https://git.kernel.org/stable/c/75b3680047bf09af8e7e471a7a6ddf2ce5847f56"}, {"url": "https://git.kernel.org/stable/c/fd238c51b0fa5390cceca9f1ac5a9ffda8063eed"}, {"url": "https://git.kernel.org/stable/c/3618b34942b76471d044369bfd30d58c39068bf1"}, {"url": "https://git.kernel.org/stable/c/97e06791368c01f0ad2a4b3269c2abe19485ca32"}, {"url": "https://git.kernel.org/stable/c/de02fc049352af5a9595f015511222d0a85c326b"}, {"url": "https://git.kernel.org/stable/c/6fe1cb312038516cb4d9fa089d700af7059f1a64"}, {"url": "https://git.kernel.org/stable/c/c0487a9c1e116cf349e2d1f302d9019670460858"}, {"url": "https://git.kernel.org/stable/c/9d5e7a46a9f6d8f503b41bfefef70659845f1679"}], "x_generator": {"engine": "bippy-1.2.0"}, "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nipv6: rpl: fix hdrlen overflow in ipv6_rpl_srh_decompress()\n\nipv6_rpl_srh_decompress() computes:\n\n outhdr->hdrlen = (((n + 1) * sizeof(struct in6_addr)) >> 3);\n\nhdrlen is __u8. For n >= 127 the result exceeds 255 and silently\ntruncates. With n=127 (cmpri=15, cmpre=15, pad=0, hdrlen=16):\n\n (128 * 16) >> 3 = 256, truncated to 0 as __u8\n\nThe caller in ipv6_rpl_srh_rcv() then places the compressed header\nat buf + ((ohdr->hdrlen + 1) << 3). With hdrlen=0 this is buf + 8,\nbut the decompressed region occupies buf[0..2055] (8-byte header\nplus 128 full addresses). The compressed header overlaps the\ndecompressed data, and ipv6_rpl_srh_compress() writes into this\noverlap, corrupting the routing header of the forwarded packet.\n\nThe existing guard at exthdrs.c:546 checks (n + 1) > 255, which\nprevents n+1 from overflowing unsigned char (the segments_left\nfield), but does not prevent the computed hdrlen from overflowing\n__u8. n=127 passes because 128 <= 255, yet hdrlen=256 does not\nfit.\n\nTighten the bound to (n + 1) > 127. This caps n at 126, giving\nhdrlen = (127 * 16) >> 3 = 254, which fits in __u8. The compressed\nheader then lands at buf + ((254 + 1) << 3) = buf + 2040, exactly\npast the decompressed region (buf[0..2039]). No overlap. 127\nsegments is well beyond any realistic RPL deployment."}], "cpeApplicability": [{"nodes": [{"negate": false, "cpeMatch": [{"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "vulnerable": true, "versionEndExcluding": "5.10.259", "versionStartIncluding": "5.7"}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "vulnerable": true, "versionEndExcluding": "5.15.210", "versionStartIncluding": "5.7"}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "vulnerable": true, "versionEndExcluding": "6.1.176", "versionStartIncluding": "5.7"}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "vulnerable": true, "versionEndExcluding": "6.6.143", "versionStartIncluding": "5.7"}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "vulnerable": true, "versionEndExcluding": "6.12.93", "versionStartIncluding": "5.7"}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "vulnerable": true, "versionEndExcluding": "6.18.35", "versionStartIncluding": "5.7"}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "vulnerable": true, "versionEndExcluding": "7.0.12", "versionStartIncluding": "5.7"}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "vulnerable": true, "versionEndExcluding": "7.1", "versionStartIncluding": "5.7"}], "operator": "OR"}]}], "providerMetadata": {"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-08-05T12:37:52.442Z"}}}, "cveMetadata": {"cveId": "CVE-2026-63984", "state": "PUBLISHED", "dateUpdated": "2026-10-19T20:18:00.765Z", "dateReserved": "2026-07-19T07:54:57.025Z", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "datePublished": "2026-07-19T14:56:06.786Z", "assignerShortName": "Linux"}, "dataVersion": "5.2"}

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"cveTags": [], "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nipv6: rpl: fix hdrlen overflow in ipv6_rpl_srh_decompress()\n\nipv6_rpl_srh_decompress() computes:\n\n outhdr->hdrlen = (((n + 1) * sizeof(struct in6_addr)) >> 3);\n\nhdrlen is __u8. For n >= 127 the result exceeds 255 and silently\ntruncates. With n=127 (cmpri=15, cmpre=15, pad=0, hdrlen=16):\n\n (128 * 16) >> 3 = 256, truncated to 0 as __u8\n\nThe caller in ipv6_rpl_srh_rcv() then places the compressed header\nat buf + ((ohdr->hdrlen + 1) << 3). With hdrlen=0 this is buf + 8,\nbut the decompressed region occupies buf[0..2055] (8-byte header\nplus 128 full addresses). The compressed header overlaps the\ndecompressed data, and ipv6_rpl_srh_compress() writes into this\noverlap, corrupting the routing header of the forwarded packet.\n\nThe existing guard at exthdrs.c:546 checks (n + 1) > 255, which\nprevents n+1 from overflowing unsigned char (the segments_left\nfield), but does not prevent the computed hdrlen from overflowing\n__u8. n=127 passes because 128 <= 255, yet hdrlen=256 does not\nfit.\n\nTighten the bound to (n + 1) > 127. This caps n at 126, giving\nhdrlen = (127 * 16) >> 3 = 254, which fits in __u8. The compressed\nheader then lands at buf + ((254 + 1) << 3) = buf + 2040, exactly\npast the decompressed region (buf[0..2039]). No overlap. 127\nsegments is well beyond any realistic RPL deployment."}], "id": "CVE-2026-63984", "lastModified": "2026-11-12T18:49:59.333", "metrics": {"cvssMetricV31": [{"cvssData": {"attackComplexity": "LOW", "attackVector": "NETWORK", "availabilityImpact": "HIGH", "baseScore": 9.8, "baseSeverity": "CRITICAL", "confidentialityImpact": "HIGH", "integrityImpact": "HIGH", "privilegesRequired": "NONE", "scope": "UNCHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H", "version": "3.1"}, "exploitabilityScore": 3.9, "impactScore": 5.9, "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "type": "Secondary"}], "ssvcV203": [{"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "ssvcData": {"id": "CVE-2026-63984", "options": [{"exploitation": "none"}, {"automatable": "yes"}, {"technicalImpact": "total"}], "role": "CISA Coordinator", "timestamp": "2026-10-16T15:34:39.184194Z", "version": "2.0.3"}}]}, "published": "2026-07-19T16:17:17.590", "references": [{"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/3618b34942b76471d044369bfd30d58c39068bf1"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/6fe1cb312038516cb4d9fa089d700af7059f1a64"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/75b3680047bf09af8e7e471a7a6ddf2ce5847f56"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/97e06791368c01f0ad2a4b3269c2abe19485ca32"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/9d5e7a46a9f6d8f503b41bfefef70659845f1679"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/c0487a9c1e116cf349e2d1f302d9019670460858"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/de02fc049352af5a9595f015511222d0a85c326b"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/fd238c51b0fa5390cceca9f1ac5a9ffda8063eed"}], "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "vulnStatus": "Analyzed", "weaknesses": [{"description": [{"lang": "en", "value": "CWE-787"}], "source": "nvd@nist.gov", "type": "Primary"}, {"description": [{"lang": "en", "value": "CWE-190"}], "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "type": "Secondary"}]}

{"bugzilla": {"description": "kernel: ipv6: rpl: fix hdrlen overflow in ipv6_rpl_srh_decompress()", "id": "2502395", "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2502395"}, "csaw": false, "cvss3": {"cvss3_base_score": "7.0", "cvss3_scoring_vector": "CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H", "status": "draft"}, "cwe": "CWE-190", "details": ["In the Linux kernel, the following vulnerability has been resolved:\nipv6: rpl: fix hdrlen overflow in ipv6_rpl_srh_decompress()\nipv6_rpl_srh_decompress() computes:\nouthdr->hdrlen = (((n + 1) * sizeof(struct in6_addr)) >> 3);\nhdrlen is __u8. For n >= 127 the result exceeds 255 and silently\ntruncates. With n=127 (cmpri=15, cmpre=15, pad=0, hdrlen=16):\n(128 * 16) >> 3 = 256, truncated to 0 as __u8\nThe caller in ipv6_rpl_srh_rcv() then places the compressed header\nat buf + ((ohdr->hdrlen + 1) << 3). With hdrlen=0 this is buf + 8,\nbut the decompressed region occupies buf[0..2055] (8-byte header\nplus 128 full addresses). The compressed header overlaps the\ndecompressed data, and ipv6_rpl_srh_compress() writes into this\noverlap, corrupting the routing header of the forwarded packet.\nThe existing guard at exthdrs.c:546 checks (n + 1) > 255, which\nprevents n+1 from overflowing unsigned char (the segments_left\nfield), but does not prevent the computed hdrlen from overflowing\n__u8. n=127 passes because 128 <= 255, yet hdrlen=256 does not\nfit.\nTighten the bound to (n + 1) > 127. This caps n at 126, giving\nhdrlen = (127 * 16) >> 3 = 254, which fits in __u8. The compressed\nheader then lands at buf + ((254 + 1) << 3) = buf + 2040, exactly\npast the decompressed region (buf[0..2039]). No overlap. 127\nsegments is well beyond any realistic RPL deployment.", "A flaw was found in the Linux kernel's IPv6 Routing Protocol for Low-Power and Lossy Networks (RPL) segment routing header (SRH) decompression function, ipv6_rpl_srh_decompress(). An integer overflow occurs when processing a specially crafted IPv6 packet, causing the header length calculation to truncate. This truncation leads to an overlap between the compressed header and decompressed data, which can result in the corruption of the routing header in forwarded packets. This vulnerability could allow a remote attacker to cause data corruption."], "name": "CVE-2026-63984", "public_date": "2026-07-19T00:00:00Z", "references": ["https://www.cve.org/CVERecord?id=CVE-2026-63984\nhttps://nvd.nist.gov/vuln/detail/CVE-2026-63984\nhttps://lore.kernel.org/linux-cve-announce/2026071902-CVE-2026-63984-8dc3@gregkh/T"], "threat_severity": "Moderate"}

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