{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2026-80978", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-08-26T14:34:25.811Z", "datePublished": "2026-09-11T19:42:39.496Z", "dateUpdated": "2026-10-19T08:46:02.787Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-10-19T08:46:02.787Z" }, "descriptions": [ { "lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet: cap advertised IP tunnel headroom\n\nIP tunnel devices derive their advertised needed_headroom from lower\noutput devices. A stack of user-created devices can make the derived\nvalue larger than the 16-bit skb header offsets can represent. Once IP\noutput reserves it, skb head expansion can wrap those offsets.\n\nThe runtime transmit path already caps a growing needed_headroom at 512.\nApply the same cap when tunnel configuration publishes needed_headroom\nderived from a lower output device.\n\nCapping the advertised value is safe: IP tunnel transmit still expands\nthe skb when a packet needs more headroom. A nonsensical stacked\nconfiguration can therefore incur an extra reallocation, but it cannot\npublish an unbounded reservation to upper layers." } ], "metrics": [ { "cvssV3_1": { "version": "3.1", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H", "baseScore": 7.8, "baseSeverity": "HIGH" }, "scenarios": [ { "lang": "en", "value": "AV:L - Triggering the wrap requires locally creating a namespace stack of IP tunnel devices (ipip/gre/sit/ip6tnl via rtnetlink or SIOCADDTUNNEL) so bind/link-config can copy an uncapped needed_headroom, then sending packets through that stack. A remote peer cannot build that topology, so the attacker-controlled path is local.\nAC:L - The attacker fully controls tunnel creation, IFLA_IPTUN_LINK/parms.link stacking (or a netkit lower device with a large IFLA_NETKIT_HEADROOM), and the subsequent transmit. Each bind copies lower needed_headroom plus t_hlen until LL_RESERVED_SPACE exceeds 16-bit skb offsets; no race or uninfluenced victim state is required.\nPR:L - Creating and binding these tunnels needs CAP_NET_ADMIN, but rtnetlink uses netlink_ns_capable()/sk_ns_capable() against net->user_ns and ip_tunnel_ctl uses ns_capable(net->user_ns, CAP_NET_ADMIN), so an unprivileged user obtains it with unshare -Urn. Fallback tunl0/ip6tnl0 devices are created in every netns by default.\nUI:N - The attacker creates the stacked tunnels and generates the traffic that drives IP output/skb_cow_head; no other user or administrator action is required.\nS:U - The resulting skb header-offset wrap corrupts kernel heap in the same OS security authority. This is standard in-kernel privilege escalation, not a VM, IOMMU, or hypervisor boundary crossing.\nC:H - After pskb_expand_head adds a >64K nhead, u16 network_header wraps so skb->data points outside skb->head. Neighbour/flow-dissect paths then __skb_pull/read with a negative offset, producing the same unbounded KASAN use-after-free/OOB read as CVE-2024-26804/CVE-2025-40173.\nI:H - Post-wrap, skb_push/dev_hard_header and iptunnel_xmit/ip6_tnl_xmit write outer IP/GRE headers at the corrupted skb->data, giving an out-of-bounds write into unrelated kernel heap that can be used for control-flow hijacking.\nA:H - The wrapped offsets and subsequent out-of-bounds accesses reliably oops/panic (KASAN, skb_under_panic, or unmapped dereference), matching the confirmed crash impact of the earlier unbounded tunnel-headroom bugs." } ] } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "include/net/ip_tunnels.h", "net/ipv4/ip_tunnel.c", "net/ipv6/ip6_gre.c", "net/ipv6/ip6_tunnel.c", "net/ipv6/sit.c" ], "versions": [ { "version": "1a37e412a0225fcba5587f24c0dfc7636efc8b69", "lessThan": "fb889a619723032140f5d983a3a34d25a5a2bed4", "status": "affected", "versionType": "git" }, { "version": "1a37e412a0225fcba5587f24c0dfc7636efc8b69", "lessThan": "b160422f8103574425e2834130e169d84c94fa1d", "status": "affected", "versionType": "git" }, { "version": "1a37e412a0225fcba5587f24c0dfc7636efc8b69", "lessThan": "d36e75f5669140b66515ad3a176ca6337bd80a5e", "status": "affected", "versionType": "git" }, { "version": "1a37e412a0225fcba5587f24c0dfc7636efc8b69", "lessThan": "84783961cb8bdb36b4f41a02ce43aafc6d52b176", "status": "affected", "versionType": "git" }, { "version": "1a37e412a0225fcba5587f24c0dfc7636efc8b69", "lessThan": "bc4e05ae66c9797a0972ac44326e69c5305e0020", "status": "affected", "versionType": "git" }, { "version": "1a37e412a0225fcba5587f24c0dfc7636efc8b69", "lessThan": "af0ee8f04bea22cdb331fa3509e17f81b48938ad", "status": "affected", "versionType": "git" }, { "version": "1a37e412a0225fcba5587f24c0dfc7636efc8b69", "lessThan": "9144f2c53a04465a6878172b523f640313c5559e", "status": "affected", "versionType": "git" }, { "version": "1a37e412a0225fcba5587f24c0dfc7636efc8b69", "lessThan": "6b222adeb9340306e2ff97127c76117abb9b3df8", "status": "affected", "versionType": "git" } ] }, { "product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "include/net/ip_tunnels.h", "net/ipv4/ip_tunnel.c", "net/ipv6/ip6_gre.c", "net/ipv6/ip6_tunnel.c", "net/ipv6/sit.c" ], "versions": [ { "version": "3.11", "status": "affected" }, { "version": "0", "lessThan": "3.11", "status": "unaffected", "versionType": "semver" }, { "version": "5.10.270", "lessThanOrEqual": "5.10.*", "status": "unaffected", "versionType": "semver" }, { "version": "5.15.221", "lessThanOrEqual": "5.15.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.1.188", "lessThanOrEqual": "6.1.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.6.157", "lessThanOrEqual": "6.6.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.12.109", "lessThanOrEqual": "6.12.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.18.50", "lessThanOrEqual": "6.18.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.2.4", "lessThanOrEqual": "7.2.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.3", "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": "3.11", "versionEndExcluding": "5.10.270" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.11", "versionEndExcluding": "5.15.221" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.11", "versionEndExcluding": "6.1.188" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.11", "versionEndExcluding": "6.6.157" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.11", "versionEndExcluding": "6.12.109" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.11", "versionEndExcluding": "6.18.50" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.11", "versionEndExcluding": "7.2.4" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "3.11", "versionEndExcluding": "7.3" } ] } ] } ], "references": [ { "url": "https://git.kernel.org/stable/c/fb889a619723032140f5d983a3a34d25a5a2bed4" }, { "url": "https://git.kernel.org/stable/c/b160422f8103574425e2834130e169d84c94fa1d" }, { "url": "https://git.kernel.org/stable/c/d36e75f5669140b66515ad3a176ca6337bd80a5e" }, { "url": "https://git.kernel.org/stable/c/84783961cb8bdb36b4f41a02ce43aafc6d52b176" }, { "url": "https://git.kernel.org/stable/c/bc4e05ae66c9797a0972ac44326e69c5305e0020" }, { "url": "https://git.kernel.org/stable/c/af0ee8f04bea22cdb331fa3509e17f81b48938ad" }, { "url": "https://git.kernel.org/stable/c/9144f2c53a04465a6878172b523f640313c5559e" }, { "url": "https://git.kernel.org/stable/c/6b222adeb9340306e2ff97127c76117abb9b3df8" } ], "title": "net: cap advertised IP tunnel headroom", "x_generator": { "engine": "bippy-1.2.0" } }, "adp": [ { "metrics": [ { "other": { "type": "ssvc", "content": { "id": "CVE-2026-80978", "role": "CISA Coordinator", "options": [ { "Exploitation": "none" }, { "Automatable": "no" }, { "Technical Impact": "total" } ], "version": "2.0.3", "timestamp": "2026-10-16T19:21:45.426777Z" } } } ], "title": "CISA ADP Vulnrichment", "providerMetadata": { "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "shortName": "CISA-ADP", "dateUpdated": "2026-10-16T19:26:37.217Z" } } ] } }