CVE-2026-63994

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which were not needed."}], "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 bug is reached when remotely injected VXLAN/GENEVE UDP packets traverse a bridged/OVS overlay and fail PMTU checks during encapsulation transmit, the same network path previously demonstrated in CVE-2023-53600 via vxlan_xmit through bridge forwarding.\nAC:L - An attacker can reliably send oversized DF-marked inner IP packets over the overlay to force PMTU ICMP generation, and can influence skb_cow() reallocation through bridge flooding/multicast cloning or headroom pressure; no uncontrollable victim state is required.\nPR:N - Exploitation requires no privileges on the victim host; any remote entity that can send VXLAN/GENEVE traffic to a VTEP with a bridged tunnel interface (standard cloud/SDN deployment) can reach the vulnerable code without authentication.\nUI:N - Triggering is fully automatic during kernel packet forwarding and tunnel encapsulation; no victim user action is needed beyond normal network operation of an overlay endpoint.\nS:U - Impact is confined to kernel memory on the affected host (UAF read/crash/potential escalation); it does not inherently cross VM, container, or IOMMU security boundaries.\nC:H - Stale ip_hdr/ipv6_hdr pointers cause reads from freed slab memory; leaked values are incorporated into ICMP error IP headers that are sent back to the attacker, constituting arbitrary kernel heap content disclosure.\nI:H - Use-after-free on skb header memory is a heap corruption primitive that can be developed into controlled writes or code execution via heap grooming, consistent with kernel UAF severity guidance.\nA:H - Dereferencing freed skb head memory during ICMP construction can cause kernel oops/panic and denial of service, as with other confirmed bugs in this same code path."}]}], "affected": 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inherently cross VM, container, or IOMMU security boundaries.\nC:H - Stale ip_hdr/ipv6_hdr pointers cause reads from freed slab memory; leaked values are incorporated into ICMP error IP headers that are sent back to the attacker, constituting arbitrary kernel heap content disclosure.\nI:H - Use-after-free on skb header memory is a heap corruption primitive that can be developed into controlled writes or code execution via heap grooming, consistent with kernel UAF severity guidance.\nA:H - Dereferencing freed skb head memory during ICMP construction can cause kernel oops/panic and denial of service, as with other confirmed bugs in this same code path."}]}], "affected": [{"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "vendor": "Linux", "product": "Linux", "versions": [{"status": "affected", "version": "4cb47a8644cc9eb8ec81190a50e79e6530d0297f", "lessThan": "95b6d772bfe788331d9742d73eaa12e113b2adc4", "versionType": "git"}, {"status": "affected", "version": 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"cveTags": [], "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\ntunnels: load network headers after skb_cow() in iptunnel_pmtud_build_icmp[v6]()\n\nSashiko found that iptunnel_pmtud_build_icmp() and\niptunnel_pmtud_build_icmpv6() were caching ip_hdr() and ipv6_hdr()\nbefore an skb_cow() call which can reallocate skb->head.\n\nFix this possible UAF by initializing the local variables\nafter the skb_cow() call.\n\nRemove skb_reset_network_header() calls which were not needed."}], "id": "CVE-2026-63994", "lastModified": "2026-10-19T21:17:17.343", "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-2026-63994", "options": [{"exploitation": "none"}, {"automatable": "yes"}, {"technicalImpact": "total"}], "role": "CISA Coordinator", "timestamp": "2026-10-16T15:34:51.504885Z", "version": "2.0.3"}}]}, "published": "2026-07-19T16:17:38.943", "references": [{"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/50750d86a2e5266aba0c295483b3397843198b11"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/6dff77899b9e9fe5d854abda3a98ad04e7229ef7"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/7254aef4d1a7e18e887af9010e2f2dc34806789b"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/76cd9398a0470257ab765bdf5f358a2af2e17934"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/95b6d772bfe788331d9742d73eaa12e113b2adc4"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/b4bc94353050b1fa7b702bd4c6600710dd926cff"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/bf8b3f34c37c162357138e7c0942723b8b94fed1"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/f3f204541f280a6ecb04503a0d6794d93990ca43"}], "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "vulnStatus": "Modified", "weaknesses": [{"description": [{"lang": "en", "value": "CWE-416"}], "source": "nvd@nist.gov", "type": "Primary"}, {"description": [{"lang": "en", "value": "CWE-416"}], "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "type": "Secondary"}]}

{"bugzilla": {"description": "kernel: tunnels: load network headers after skb_cow() in iptunnel_pmtud_build_icmp[v6]()", "id": "2502444", "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2502444"}, "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-825", "details": ["In the Linux kernel, the following vulnerability has been resolved:\ntunnels: load network headers after skb_cow() in iptunnel_pmtud_build_icmp[v6]()\nSashiko found that iptunnel_pmtud_build_icmp() and\niptunnel_pmtud_build_icmpv6() were caching ip_hdr() and ipv6_hdr()\nbefore an skb_cow() call which can reallocate skb->head.\nFix this possible UAF by initializing the local variables\nafter the skb_cow() call.\nRemove skb_reset_network_header() calls which were not needed.", "A flaw was found in the Linux kernel's tunnels module. This vulnerability, categorized as a Use-After-Free (UAF), arises from improper handling of network header pointers during certain packet processing operations. Specifically, functions responsible for building Internet Control Message Protocol (ICMP) packets for Path MTU Discovery (PMTUD) cache header information before memory reallocations, which can lead to the use of freed memory. A local attacker could potentially leverage this to cause a system crash, resulting in a denial of service."], "name": "CVE-2026-63994", "package_state": [{"cpe": "cpe:/o:redhat:enterprise_linux:10", "fix_state": "Affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 10"}, {"cpe": "cpe:/o:redhat:enterprise_linux:6", "fix_state": "Under investigation", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 6"}, {"cpe": "cpe:/o:redhat:enterprise_linux:7", "fix_state": "Not affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 7"}, {"cpe": "cpe:/o:redhat:enterprise_linux:7", "fix_state": "Not affected", "package_name": "kernel-rt", "product_name": "Red Hat Enterprise Linux 7"}, {"cpe": "cpe:/o:redhat:enterprise_linux:8", "fix_state": "Affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 8"}, {"cpe": "cpe:/o:redhat:enterprise_linux:8", "fix_state": "Affected", "package_name": "kernel-rt", "product_name": "Red Hat Enterprise Linux 8"}, {"cpe": "cpe:/o:redhat:enterprise_linux:9", "fix_state": "Affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 9"}, {"cpe": "cpe:/o:redhat:enterprise_linux:9", "fix_state": "Affected", "package_name": "kernel-rt", "product_name": "Red Hat Enterprise Linux 9"}, {"cpe": "cpe:/a:redhat:hummingbird:1", "fix_state": "Not affected", "impact": "important", "package_name": "erlang27", "product_name": "Red Hat Hardened Images"}], "public_date": "2026-07-19T00:00:00Z", "references": ["https://www.cve.org/CVERecord?id=CVE-2026-63994\nhttps://nvd.nist.gov/vuln/detail/CVE-2026-63994\nhttps://lore.kernel.org/linux-cve-announce/2026071905-CVE-2026-63994-97bf@gregkh/T"], "threat_severity": "Important"}

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