{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2026-89555", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-09-11T19:38:34.724Z", "datePublished": "2026-09-11T19:44:28.331Z", "dateUpdated": "2026-10-19T08:48:48.093Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-10-19T08:48:48.093Z" }, "descriptions": [ { "lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nmpls: reload header after pskb_may_pull()\n\nmpls_select_multipath() calls mpls_multipath_hash() to choose a nexthop\nwhen an MPLS route has multiple nexthops. While walking the MPLS label\nstack, the hash routine caches hdr for the current label. After finding\nthe bottom-of-stack label, it calls pskb_may_pull() before reading the\ninner IP header.\n\nIf an skb is constructed with the inner IP header in nonlinear data and\ninsufficient tailroom in the linear head, pskb_may_pull() calls\npskb_expand_head() to replace the skb head and free the old one. This\nleaves hdr pointing to freed memory. The IPv6 path can invalidate hdr\nagain when it performs a second pull for the larger header.\n\nThe issue was found through static analysis. A reproducer sending a legal\nGeneve packet through a bareudp/MPLS multipath setup triggered the same\nKASAN report in 2 of 2 unpatched runs:\n\n BUG: KASAN: slab-use-after-free in mpls_select_multipath\n Read of size 1 at addr ffff88800ecc6e20 by task ksoftirqd/1/23\n\n Call Trace:\n mpls_select_multipath\n mpls_forward\n __netif_receive_skb_list_core\n netif_receive_skb_list_internal\n napi_complete_done\n gro_cell_poll\n __napi_poll\n net_rx_action\n\n Freed by task 23:\n kfree\n pskb_expand_head\n __pskb_pull_tail\n mpls_select_multipath\n\nReload hdr from the current skb head after each successful pull before\nderiving the inner IPv4 or IPv6 header pointer." } ], "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 - mpls_forward() is the ETH_P_MPLS_UC packet_type receive handler; remote MPLS-in-IP (IPPROTO_MPLS), MPLS-over-UDP/bareudp, Geneve, and IPIP/SIT/ip6 tunnels deliver inner MPLS into this path without local access, matching the Geneve/bareudp KASAN reproducer.\nAC:L - An attacker sending MPLS or tunneled overlay frames fully controls the label stack, BOS bit, and skb layout; GRO/tunnel decap yields nonlinear skbs so pskb_may_pull() reallocates skb->head, and the unpatched Geneve reproducer hit the UAF in 2 of 2 runs with no victim-timed race.\nPR:N - Exploitation needs only unauthenticated packets that hit an already configured MPLS-enabled interface and multipath label route; mpls_forward() performs no credential check, and enabling MPLS input or tunnels is victim deployment rather than an attacker privilege.\nUI:N - The use-after-free runs in softirq receive processing (gro_cell_poll / netif_receive_skb_list) as soon as the crafted frame is accepted; no local user or administrator action is required beyond normal forwarding.\nS:U - The stale MPLS header pointer is a heap use-after-free inside the same host kernel MPLS forwarding path; impact stays within that kernel security authority and does not cross a VM, IOMMU, or other boundary.\nC:H - After pskb_expand_head() frees the old skb head, mpls_multipath_hash() reads the inner IPv4/IPv6 header through the stale hdr pointer, a slab use-after-free that can disclose freed kmalloc contents and is scored as high-impact kernel information disclosure.\nI:H - The immediate stale access is a header read used for ECMP hashing, but it remains a kernel slab use-after-free of skb->head; attacker-controlled reclaim of the freed kmalloc object is a well-established path to heap corruption and control-flow hijacking.\nA:H - KASAN confirmed a slab-use-after-free in mpls_select_multipath() on the forwarding path; dereferencing the freed skb head can oops or panic the kernel, and UAFs remain a high-impact denial of service even without full exploitation." } ] } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "net/mpls/af_mpls.c" ], "versions": [ { "version": "9f427a0e474a67b454420c131709600d44850486", "lessThan": "aa4fe0b450a461aa1162fe8375f5d28f4c957df8", "status": "affected", "versionType": "git" }, { "version": "9f427a0e474a67b454420c131709600d44850486", "lessThan": "b1c0783b2facc398437ad8f8b86c636d7a78f8db", "status": "affected", "versionType": "git" }, { "version": "9f427a0e474a67b454420c131709600d44850486", "lessThan": "bfaaff99238326166694354a63a76c02563f98b1", "status": "affected", "versionType": "git" }, { "version": "9f427a0e474a67b454420c131709600d44850486", "lessThan": "d9640239827d6d0cb84263b590f7a4f1596c17eb", "status": "affected", "versionType": "git" }, { "version": "9f427a0e474a67b454420c131709600d44850486", "lessThan": "fed638a248116b8a249bd4202d28e5934bdc65ad", "status": "affected", "versionType": "git" }, { "version": "9f427a0e474a67b454420c131709600d44850486", "lessThan": "d82b90a38c2ca8a0694428eab0e9551c23f2447d", "status": "affected", "versionType": "git" }, { "version": "9f427a0e474a67b454420c131709600d44850486", "lessThan": "49d38c1b4390412f8950d33dfaee0ccbd17beb81", "status": "affected", "versionType": "git" }, { "version": "9f427a0e474a67b454420c131709600d44850486", "lessThan": "29e63b8d9fc150cc191b1c6eb7e16e1247e1b650", "status": "affected", "versionType": "git" }, { "version": "ad864d9fce0ec56cc8f6afe5c6a0e6d7f484b9eb", "status": "affected", "versionType": "git" }, { "version": "4.9.8", "lessThan": "4.10", "status": "affected", "versionType": "semver" } ] }, { "product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "net/mpls/af_mpls.c" ], "versions": [ { "version": "4.10", "status": "affected" }, { "version": "0", "lessThan": "4.10", "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": "4.10", "versionEndExcluding": "5.10.270" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.10", "versionEndExcluding": "5.15.221" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.10", "versionEndExcluding": "6.1.188" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.10", "versionEndExcluding": "6.6.157" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.10", "versionEndExcluding": "6.12.109" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.10", "versionEndExcluding": "6.18.50" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.10", "versionEndExcluding": "7.2.4" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.10", "versionEndExcluding": "7.3" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.9.8" } ] } ] } ], "references": [ { "url": "https://git.kernel.org/stable/c/aa4fe0b450a461aa1162fe8375f5d28f4c957df8" }, { "url": "https://git.kernel.org/stable/c/b1c0783b2facc398437ad8f8b86c636d7a78f8db" }, { "url": "https://git.kernel.org/stable/c/bfaaff99238326166694354a63a76c02563f98b1" }, { "url": "https://git.kernel.org/stable/c/d9640239827d6d0cb84263b590f7a4f1596c17eb" }, { "url": "https://git.kernel.org/stable/c/fed638a248116b8a249bd4202d28e5934bdc65ad" }, { "url": "https://git.kernel.org/stable/c/d82b90a38c2ca8a0694428eab0e9551c23f2447d" }, { "url": "https://git.kernel.org/stable/c/49d38c1b4390412f8950d33dfaee0ccbd17beb81" }, { "url": "https://git.kernel.org/stable/c/29e63b8d9fc150cc191b1c6eb7e16e1247e1b650" } ], "title": "mpls: reload header after pskb_may_pull()", "x_generator": { "engine": "bippy-1.2.0" } }, "adp": [ { "metrics": [ { "other": { "type": "ssvc", "content": { "id": "CVE-2026-89555", "role": "CISA Coordinator", "options": [ { "Exploitation": "none" }, { "Automatable": "yes" }, { "Technical Impact": "total" } ], "version": "2.0.3", "timestamp": "2026-10-16T19:24:02.263001Z" } } } ], "title": "CISA ADP Vulnrichment", "providerMetadata": { "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "shortName": "CISA-ADP", "dateUpdated": "2026-10-16T19:26:43.764Z" } } ] } }