{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2026-63994", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-07-19T07:54:57.026Z", "datePublished": "2026-07-19T14:56:13.896Z", "dateUpdated": "2026-08-05T12:37:58.389Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-08-05T12:37:58.389Z" }, "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." } ], "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": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "net/ipv4/ip_tunnel_core.c" ], "versions": [ { "version": "4cb47a8644cc9eb8ec81190a50e79e6530d0297f", "lessThan": "95b6d772bfe788331d9742d73eaa12e113b2adc4", "status": "affected", "versionType": "git" }, { "version": "4cb47a8644cc9eb8ec81190a50e79e6530d0297f", "lessThan": "7254aef4d1a7e18e887af9010e2f2dc34806789b", "status": "affected", "versionType": "git" }, { "version": "4cb47a8644cc9eb8ec81190a50e79e6530d0297f", "lessThan": "bf8b3f34c37c162357138e7c0942723b8b94fed1", "status": "affected", "versionType": "git" }, { "version": "4cb47a8644cc9eb8ec81190a50e79e6530d0297f", "lessThan": "76cd9398a0470257ab765bdf5f358a2af2e17934", "status": "affected", "versionType": "git" }, { "version": "4cb47a8644cc9eb8ec81190a50e79e6530d0297f", "lessThan": "50750d86a2e5266aba0c295483b3397843198b11", "status": "affected", "versionType": "git" }, { "version": "4cb47a8644cc9eb8ec81190a50e79e6530d0297f", "lessThan": "6dff77899b9e9fe5d854abda3a98ad04e7229ef7", "status": "affected", "versionType": "git" }, { "version": "4cb47a8644cc9eb8ec81190a50e79e6530d0297f", "lessThan": "f3f204541f280a6ecb04503a0d6794d93990ca43", "status": "affected", "versionType": "git" }, { "version": "4cb47a8644cc9eb8ec81190a50e79e6530d0297f", "lessThan": "b4bc94353050b1fa7b702bd4c6600710dd926cff", "status": "affected", "versionType": "git" } ] }, { "product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "net/ipv4/ip_tunnel_core.c" ], "versions": [ { "version": "5.9", "status": "affected" }, { "version": "0", "lessThan": "5.9", "status": "unaffected", "versionType": "semver" }, { "version": "5.10.259", "lessThanOrEqual": "5.10.*", "status": "unaffected", "versionType": "semver" }, { "version": "5.15.210", "lessThanOrEqual": "5.15.*", "status": "unaffected", "versionType": "semver" }, { "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": "5.9", "versionEndExcluding": "5.10.259" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.9", "versionEndExcluding": "5.15.210" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.9", "versionEndExcluding": "6.1.176" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.9", "versionEndExcluding": "6.6.143" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.9", "versionEndExcluding": "6.12.93" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.9", "versionEndExcluding": "6.18.35" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.9", "versionEndExcluding": "7.0.12" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.9", "versionEndExcluding": "7.1" } ] } ] } ], "references": [ { "url": "https://git.kernel.org/stable/c/95b6d772bfe788331d9742d73eaa12e113b2adc4" }, { "url": "https://git.kernel.org/stable/c/7254aef4d1a7e18e887af9010e2f2dc34806789b" }, { "url": "https://git.kernel.org/stable/c/bf8b3f34c37c162357138e7c0942723b8b94fed1" }, { "url": "https://git.kernel.org/stable/c/76cd9398a0470257ab765bdf5f358a2af2e17934" }, { "url": "https://git.kernel.org/stable/c/50750d86a2e5266aba0c295483b3397843198b11" }, { "url": "https://git.kernel.org/stable/c/6dff77899b9e9fe5d854abda3a98ad04e7229ef7" }, { "url": "https://git.kernel.org/stable/c/f3f204541f280a6ecb04503a0d6794d93990ca43" }, { "url": "https://git.kernel.org/stable/c/b4bc94353050b1fa7b702bd4c6600710dd926cff" } ], "title": "tunnels: load network headers after skb_cow() in iptunnel_pmtud_build_icmp[v6]()", "x_generator": { "engine": "bippy-1.2.0" } } } }