CVE-2026-63993

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through the VXLAN device.\nS:U - The vulnerability corrupts kernel heap memory on the host processing the VXLAN traffic; impact remains within the kernel's security authority and does not inherently cross a VM or sandbox boundary.\nC:H - This is a use-after-free where ip_tunnel_ecn_encap() reads from a freed skb head via the stale cached ip_hdr pointer, enabling kernel memory disclosure and supporting further exploitation.\nI:H - Use-after-free on skb data provides a foundation for heap grooming and arbitrary memory write primitives that could be leveraged for kernel code execution or privilege escalation.\nA:H - The UAF can cause kernel oops/panic during transmit processing and is independently exploitable for denial of service even when full code execution is not achieved."}]}], "affected": [{"product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": 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"https://git.kernel.org/stable/c/8d435d68d71fb875876b722f4136caf74f2f48bd"}, {"url": "https://git.kernel.org/stable/c/dc3bfa050f873371e745bdf478b1f5b738e5733d"}, {"url": "https://git.kernel.org/stable/c/609e63312c29aad18026a1d3222e123d4b6b0feb"}, {"url": "https://git.kernel.org/stable/c/5303925e360527243b46a440a04667826bbc72b7"}, {"url": "https://git.kernel.org/stable/c/a493efd4336cf19122ae0e4cbb3d31b32d70deea"}, {"url": "https://git.kernel.org/stable/c/7d9ef0cb271555d8cf39fefe6c981e1493b25ecf"}], "title": "vxlan: do not reuse cached ip_hdr() value after skb_tunnel_check_pmtu()", "x_generator": {"engine": "bippy-1.2.0"}}, "adp": [{"metrics": [{"other": {"type": "ssvc", "content": {"id": "CVE-2026-63993", "role": "CISA Coordinator", "options": [{"Exploitation": "none"}, {"Automatable": "yes"}, {"Technical Impact": "total"}], "version": "2.0.3", "timestamp": "2026-10-16T15:34:49.188699Z"}}}], "problemTypes": [{"descriptions": [{"lang": "en", "type": "CWE", "cweId": "CWE-416", 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decapsulated, bridged, and re-encapsulated; VXLAN is a UDP-based overlay protocol reachable from remote peers over the network.\nAC:L - An attacker can reliably trigger the bug by sending crafted oversized inner IPv4/IPv6 packets (e.g., with DF set or ICMP/ICMPv6 payloads) through a bridged VXLAN interface to force skb_tunnel_check_pmtu() to reallocate skb->head yet return 0, leaving the cached ip_hdr pointer stale.\nPR:N - Exploitation requires only the ability to send VXLAN/inner IP traffic to a host with an active VXLAN bridge port; no local account, capabilities, or authentication on the victim is needed.\nUI:N - No victim user action is required beyond normal network operation; triggering the bug is entirely driven by attacker-supplied packets forwarded through the VXLAN device.\nS:U - The vulnerability corrupts kernel heap memory on the host processing the VXLAN traffic; impact remains within the kernel's security authority and does not inherently cross a VM or sandbox boundary.\nC:H - This is a use-after-free where ip_tunnel_ecn_encap() reads from a freed skb head via the stale cached ip_hdr pointer, enabling kernel memory disclosure and supporting further exploitation.\nI:H - Use-after-free on skb data provides a foundation for heap grooming and arbitrary memory write primitives that could be leveraged for kernel code execution or privilege escalation.\nA:H - The UAF can cause kernel oops/panic during transmit processing and is independently exploitable for denial of service even when full code execution is not achieved."}]}], "affected": [{"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "vendor": "Linux", "product": "Linux", "versions": [{"status": "affected", "version": "4cb47a8644cc9eb8ec81190a50e79e6530d0297f", "lessThan": "6b8bfce9d2f774d2c2243e0248e03efb99bba6c0", "versionType": "git"}, {"status": "affected", "version": "4cb47a8644cc9eb8ec81190a50e79e6530d0297f", "lessThan": 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"416baaa9-dc9f-4396-8d5f-8c081fb06d67", "type": "Secondary"}], "ssvcV203": [{"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "ssvcData": {"id": "CVE-2026-63993", "options": [{"exploitation": "none"}, {"automatable": "yes"}, {"technicalImpact": "total"}], "role": "CISA Coordinator", "timestamp": "2026-10-16T15:34:49.188699Z", "version": "2.0.3"}}]}, "published": "2026-07-19T16:17:38.823", "references": [{"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/5303925e360527243b46a440a04667826bbc72b7"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/609e63312c29aad18026a1d3222e123d4b6b0feb"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/6b8bfce9d2f774d2c2243e0248e03efb99bba6c0"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": 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"type": "Secondary"}]}

{"bugzilla": {"description": "kernel: vxlan: do not reuse cached ip_hdr() value after skb_tunnel_check_pmtu()", "id": "2502369", "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2502369"}, "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:\nvxlan: do not reuse cached ip_hdr() value after skb_tunnel_check_pmtu()\nskb_tunnel_check_pmtu() can change skb->head.\nReusing old_iph afer skb_tunnel_check_pmtu() can cause an UAF.\nUse instead ip_hdr(skb) as done in drivers/net/bareudp.c\nand drivers/net/geneve.c.\nFound by Sashiko.", "A flaw was found in the Linux kernel's Virtual Extensible LAN (VXLAN) module. This vulnerability occurs because a cached IP header pointer is improperly reused after a Path Maximum Transmission Unit (PMTU) check. When the packet's head is modified during the PMTU check, the old cached IP header pointer becomes invalid, leading to a Use-After-Free (UAF) condition. This memory corruption flaw can potentially allow an attacker to cause a system crash or execute arbitrary code."], "name": "CVE-2026-63993", "package_state": [{"cpe": "cpe:/o:redhat:enterprise_linux:10", "fix_state": "Fix deferred", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 10"}, {"cpe": "cpe:/o:redhat:enterprise_linux:6", "fix_state": "Not affected", "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": "Not affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 8"}, {"cpe": "cpe:/o:redhat:enterprise_linux:8", "fix_state": "Not affected", "package_name": "kernel-rt", "product_name": "Red Hat Enterprise Linux 8"}, {"cpe": "cpe:/o:redhat:enterprise_linux:9", "fix_state": "Fix deferred", "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-2026-63993\nhttps://nvd.nist.gov/vuln/detail/CVE-2026-63993\nhttps://lore.kernel.org/linux-cve-announce/2026071905-CVE-2026-63993-165e@gregkh/T"], "threat_severity": "Important"}

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