{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2026-68297", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-07-30T09:28:09.380Z", "datePublished": "2026-08-10T12:02:30.721Z", "dateUpdated": "2026-08-19T16:32:46.091Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-08-19T16:32:46.091Z" }, "descriptions": [ { "lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\ntipc: fix u16 MTU truncation in media and bearer MTU validation\n\nBoth TIPC_NL_MEDIA_SET and TIPC_NL_BEARER_SET accept user-supplied\nMTU values but only enforce a minimum bound, not a maximum. When a user\nsets the MTU to a value exceeding U16_MAX (65535), it passes validation\nbut is silently truncated when assigned to u16 fields l->mtu and\nl->advertised_mtu in tipc_link_create(). Values like 65536 (0x10000)\ntruncate to 0, causing a division by zero in tipc_link_set_queue_limits()\nwhich computes TIPC_MAX_PUBL / (l->mtu / ITEM_SIZE). Other overflowing\nvalues (e.g. 65537-131071) produce small incorrect MTU values, resulting\nin link malfunction behaviors.\n\nCrash stack (triggered as unprivileged user via user namespace):\n\n tipc_link_set_queue_limits net/tipc/link.c:2531\n tipc_link_create net/tipc/link.c:520\n tipc_node_check_dest net/tipc/node.c:1279\n tipc_disc_rcv net/tipc/discover.c:252\n tipc_rcv net/tipc/node.c:2129\n tipc_udp_recv net/tipc/udp_media.c:392\n\nTwo independent paths lack the upper bound check:\n1. tipc_udp_mtu_bad() -- called from __tipc_nl_media_set() (MEDIA_SET)\n2. inline check in __tipc_nl_bearer_set() at bearer.c:1160 (BEARER_SET)\n\nFix both by rejecting MTU values above U16_MAX." } ], "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 - The attack begins with a local TIPC netlink command (TIPC_NL_BEARER_SET/TIPC_NL_MEDIA_SET) setting an out-of-range MTU, with the crash/corruption then triggered by locally generated discovery traffic and sendmsg() in the attacker's own network namespace.\nAC:L - The attacker fully controls both the bad MTU value and the discovery packet that creates the link, so the truncation and subsequent divide-by-zero or undersized-fragment path trigger deterministically on every attempt.\nPR:L - Both netlink ops are gated by GENL_UNS_ADMIN_PERM, i.e. CAP_NET_ADMIN in the owning user namespace, which any unprivileged user obtains via `unshare -Urn`; the commit message explicitly reports the crash reproduced as an unprivileged user through a user namespace.\nUI:N - The attacker performs every step (bearer setup, MTU configuration, packet injection, sendmsg) with no action from any other user or administrator.\nS:U - The truncated MTU corrupts only kernel state within the same kernel security authority; no VM, IOMMU, or sandbox boundary is crossed.\nC:H - Truncated MTUs below the TIPC header size propagate into tipc_msg_build() as pktmax, driving negative fragment remainders and oversized copies into undersized skbs; the resulting heap corruption and adjacent-object exposure can be leveraged to read kernel memory.\nI:H - The undersized-fragment path writes INT_H_SIZE plus header bytes and then a negative-length (huge unsigned) user copy into a buffer allocated at the truncated MTU size, giving an attacker-controlled linear heap overflow suitable for control-flow hijacking.\nA:H - MTU values truncating to under 20 make tipc_link_set_queue_limits() divide by zero inside tipc_link_create(), which runs in softirq context from tipc_udp_recv()/tipc_disc_rcv(), producing a kernel oops that is typically fatal in interrupt context." } ] } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "net/tipc/netlink.c" ], "versions": [ { "version": "901271e0403af638c224987c2a4e55cebade7e91", "lessThan": "8bfdfe0dbb36a650b7c4dec1aeae078319938a0b", "status": "affected", "versionType": "git" }, { "version": "901271e0403af638c224987c2a4e55cebade7e91", "lessThan": "dc4b577a083b361d25e118dc96d8281255ebe22c", "status": "affected", "versionType": "git" }, { "version": "901271e0403af638c224987c2a4e55cebade7e91", "lessThan": "dfdfd987f1917c84766e097a6120a1f3f1634940", "status": "affected", "versionType": "git" }, { "version": "901271e0403af638c224987c2a4e55cebade7e91", "lessThan": "f02334a9e378f7e07232b26dc3d2ab353339f040", "status": "affected", "versionType": "git" }, { "version": "901271e0403af638c224987c2a4e55cebade7e91", "lessThan": "f4013598b69457dbea350df52e52daea6faef8eb", "status": "affected", "versionType": "git" }, { "version": "901271e0403af638c224987c2a4e55cebade7e91", "lessThan": "1b8fb5a20508bfb0db854e01214888c761b3a911", "status": "affected", "versionType": "git" }, { "version": "901271e0403af638c224987c2a4e55cebade7e91", "lessThan": "c1cda72f6acec02ebd45d913bf8527ff77336ba6", "status": "affected", "versionType": "git" }, { "version": "901271e0403af638c224987c2a4e55cebade7e91", "lessThan": "9f29cd8a8e7901a2617c8064ce9f50fc67b97cb8", "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/tipc/netlink.c" ], "versions": [ { "version": "4.18", "status": "affected" }, { "version": "0", "lessThan": "4.18", "status": "unaffected", "versionType": "semver" }, { "version": "5.10.265", "lessThanOrEqual": "5.10.*", "status": "unaffected", "versionType": "semver" }, { "version": "5.15.216", "lessThanOrEqual": "5.15.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.1.183", "lessThanOrEqual": "6.1.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.6.148", "lessThanOrEqual": "6.6.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.12.101", "lessThanOrEqual": "6.12.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.18.42", "lessThanOrEqual": "6.18.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.1.6", "lessThanOrEqual": "7.1.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.2", "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": "4.18", "versionEndExcluding": "5.10.265" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.18", "versionEndExcluding": "5.15.216" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.18", "versionEndExcluding": "6.1.183" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.18", "versionEndExcluding": "6.6.148" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.18", "versionEndExcluding": "6.12.101" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.18", "versionEndExcluding": "6.18.42" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.18", "versionEndExcluding": "7.1.6" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.18", "versionEndExcluding": "7.2" } ] } ] } ], "references": [ { "url": "https://git.kernel.org/stable/c/8bfdfe0dbb36a650b7c4dec1aeae078319938a0b" }, { "url": "https://git.kernel.org/stable/c/dc4b577a083b361d25e118dc96d8281255ebe22c" }, { "url": "https://git.kernel.org/stable/c/dfdfd987f1917c84766e097a6120a1f3f1634940" }, { "url": "https://git.kernel.org/stable/c/f02334a9e378f7e07232b26dc3d2ab353339f040" }, { "url": "https://git.kernel.org/stable/c/f4013598b69457dbea350df52e52daea6faef8eb" }, { "url": "https://git.kernel.org/stable/c/1b8fb5a20508bfb0db854e01214888c761b3a911" }, { "url": "https://git.kernel.org/stable/c/c1cda72f6acec02ebd45d913bf8527ff77336ba6" }, { "url": "https://git.kernel.org/stable/c/9f29cd8a8e7901a2617c8064ce9f50fc67b97cb8" } ], "title": "tipc: fix u16 MTU truncation in media and bearer MTU validation", "x_generator": { "engine": "bippy-1.2.0" } } } }