{"id":"CVE-2026-89651","title":"ceph: bound MDSCapAuth path and fs_name decode in handle_session()","summary":"In the Linux kernel, the following vulnerability has been resolved:\n\nceph: bound MDSCapAuth path and fs_name decode in handle_session()\n\nhandle_session() decodes the MDSCapAuth records carried by a\nCEPH_SESSION_OPEN message (msg_version …","severity":"critical","cvss":9.8,"cvssVector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","cvssSource":"cna","cwe":["CWE-125"],"vendor":"Linux","product":"Linux","affected":["Linux >= 1d17de9534cb5a4c4c380d174cc2f9281b34f89e < dc5c7dffda92ef372fa587c444a1c537373df824","Linux >= 1d17de9534cb5a4c4c380d174cc2f9281b34f89e < c37db86d2b5e9b57001ccae7e7a727e95a4f9c02","Linux >= 1d17de9534cb5a4c4c380d174cc2f9281b34f89e < 5f892c767b30e4fb0c744c59f9235c717383d2cd","Linux >= 1d17de9534cb5a4c4c380d174cc2f9281b34f89e < 77933e22adfe813be2bd10be08d6e950103c3967","Linux 6.10"],"published":"2026-09-11","updated":"2026-10-19","sourceUpdated":"2026-10-19T08:50:22.893Z","source":"CVEORG","sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-89651","references":[{"url":"https://git.kernel.org/stable/c/dc5c7dffda92ef372fa587c444a1c537373df824"},{"url":"https://git.kernel.org/stable/c/c37db86d2b5e9b57001ccae7e7a727e95a4f9c02"},{"url":"https://git.kernel.org/stable/c/5f892c767b30e4fb0c744c59f9235c717383d2cd"},{"url":"https://git.kernel.org/stable/c/77933e22adfe813be2bd10be08d6e950103c3967"},{"url":"https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-89651.json"},{"url":"https://access.redhat.com/security/cve/CVE-2026-89651"},{"url":"https://bugzilla.redhat.com/show_bug.cgi?id=2532282"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-89651"},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-89651"},{"url":"https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-89651.mbox"}],"tags":["cve.org","csaf","vex","red-hat","score-dispute"],"epss":0.00635,"epssPercentile":0.50213,"scores":{"cna":9.8,"vendor":7},"ingestedAt":"2026-09-14T15:23:07.473Z","slug":"CVE-2026-89651","body":"## Overview\n\nIn the Linux kernel, the following vulnerability has been resolved:\n\nceph: bound MDSCapAuth path and fs_name decode in handle_session()\n\nhandle_session() decodes the MDSCapAuth records carried by a\nCEPH_SESSION_OPEN message (msg_version >= 6). For each record the\nmatch.path and match.fs_name byte strings are read by first decoding a\n32-bit length and then copying that many bytes with the bare\nceph_decode_copy(). Unlike the surrounding fields, which all use the\n_safe decode variants, these two copies are not preceded by a\nceph_decode_need() bounds check, and the enclosing MDSCapAuth and\nMDSCapMatch struct_len fields are skipped rather than enforced as an\nupper bound. A length larger than the bytes remaining in the message\nfront makes ceph_decode_copy() read past the end of the front buffer.\n\nThe message front is a dedicated allocation (ceph_msg_new2() ->\nkvmalloc), so the over-read runs off that object. A malicious or\ncompromised MDS can trigger this with the first post-connect message on\nmount, with no client-side user interaction; under KASAN it is reported\nas a slab-out-of-bounds read in handle_session().\n\nImpact: a malicious MDS can force the kernel client to read up to 4 GiB\npast the message front allocation during session setup, crashing the\nclient (out-of-bounds read).\n\nSwitch both copies to ceph_decode_copy_safe(), which performs the\nceph_decode_need() bounds check before the copy and branches to the\nexisting bad label, matching the rest of the decoder and the error path\nthat frees the partially decoded cap_auths array.\n\n## Affected\n\n- `Linux >= 1d17de9534cb5a4c4c380d174cc2f9281b34f89e < dc5c7dffda92ef372fa587c444a1c537373df824`\n- `Linux >= 1d17de9534cb5a4c4c380d174cc2f9281b34f89e < c37db86d2b5e9b57001ccae7e7a727e95a4f9c02`\n- `Linux >= 1d17de9534cb5a4c4c380d174cc2f9281b34f89e < 5f892c767b30e4fb0c744c59f9235c717383d2cd`\n- `Linux >= 1d17de9534cb5a4c4c380d174cc2f9281b34f89e < 77933e22adfe813be2bd10be08d6e950103c3967`\n- `Linux 6.10`\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.\n\n## Vendor advisories\n\n- **Red Hat VEX** · Moderate · affected: Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 9 · no fix planned: Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 9 · updated 2026-09-18 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-89651.json)","depth":"midnight","depthScore":54,"depthScoreParts":{"impact":53.9,"likelihood":0.1,"exploitation":0,"ransomware":0},"changes":[{"seq":224644,"id":"CVE-2026-89651","ts":1792401453412,"field":"cvss","old":"7","new":"9.8"},{"seq":224643,"id":"CVE-2026-89651","ts":1792401453412,"field":"severity","old":"high","new":"critical"},{"seq":208120,"id":"CVE-2026-89651","ts":1789922716655,"field":"cvss","old":"5.9","new":"7"},{"seq":208119,"id":"CVE-2026-89651","ts":1789922716655,"field":"severity","old":"medium","new":"high"},{"seq":203001,"id":"CVE-2026-89651","ts":1789403733300,"field":"cvss","old":"9.8","new":"5.9"},{"seq":203000,"id":"CVE-2026-89651","ts":1789403733300,"field":"severity","old":"critical","new":"medium"},{"seq":197801,"id":"CVE-2026-89651","ts":1789384318916,"field":"cvss","old":"5.9","new":"9.8"},{"seq":197800,"id":"CVE-2026-89651","ts":1789384318916,"field":"severity","old":"medium","new":"critical"},{"seq":183715,"id":"CVE-2026-89651","ts":1789356677076,"field":"cvss","old":"9.8","new":"5.9"},{"seq":183714,"id":"CVE-2026-89651","ts":1789356677076,"field":"severity","old":"critical","new":"medium"},{"seq":153500,"id":"CVE-2026-89651","ts":1789285350814,"field":"cvss","old":null,"new":"9.8"},{"seq":153499,"id":"CVE-2026-89651","ts":1789285350814,"field":"severity","old":"none","new":"critical"},{"seq":147462,"id":"CVE-2026-89651","ts":1789270211003,"field":"cvss","old":null,"new":"5.9"},{"seq":147461,"id":"CVE-2026-89651","ts":1789270211003,"field":"severity","old":"none","new":"medium"},{"seq":109218,"id":"CVE-2026-89651","ts":1789183730771,"field":"cvss","old":null,"new":"5.9"},{"seq":109217,"id":"CVE-2026-89651","ts":1789183730771,"field":"severity","old":"none","new":"medium"}]}