CVE-2026-89651

CVE CVE-2026-89651EUVD EUVD-2026-76563Published 2026-09-11T19:45:41.000ZLast changed 2026-09-13T06:32:30.000ZCVSS 9.8

What the advisory describes

In the Linux kernel, the following vulnerability has been resolved: ceph: bound MDSCapAuth path and fs_name decode in handle_session() handle_session() decodes the MDSCapAuth records carried by a CEPH_SESSION_OPEN message (msg_version >= 6). For each record the match.path and match.fs_name byte strings are read by first decoding a 32-bit length and then copying that many bytes with the bare ceph_decode_copy(). Unlike the surrounding fields, which all use the _safe decode variants, these two copies are not preceded by a ceph_decode_need() bounds check, and the enclosing MDSCapAuth and MDSCapMatch struct_len fields are skipped rather than enforced as an upper bound. A length larger than the bytes remaining in the message front makes ceph_decode_copy() read past the end of the front buffer. The message front is a dedicated allocation (ceph_msg_new2() -> kvmalloc), so the over-read runs off that object. A malicious or compromised MDS can trigger this with the first post-connect message on mount, with no client-side user interaction; under KASAN it is reported as a slab-out-of-bounds read in handle_session(). Impact: a malicious MDS can force the kernel client to read up to 4 GiB past the message front allocation during session setup, crashing the client (out-of-bounds read). Switch both copies to ceph_decode_copy_safe(), which performs the ceph_decode_need() bounds check before the copy and branches to the existing bad label, matching the rest of the decoder and the error path that frees the partially decoded cap_auths array.

Source: EUVD (ENISA), in the words of the advisory.

Products the advisory names

These come from the advisory itself, not from any check we performed.

• Linux — Linux 1d17de9534cb5a4c4c380d174cc2f9281b34f89e <c37db86d2b5e9b57001ccae7e7a727e95a4f9c02; patch: 6.12.109; patch: 0; patch: 7.2.4; 1d17de9534cb5a4c4c380d174cc2f9281b34f89e <dc5c7dffda92ef372fa587c444a1c537373df824; patch: 6.18.50; 6.10; patch: 7.3-rc1; 1d17de9534cb5a4c4c380d174cc2f9281b34f89e <5f892c767b30e4fb0c744c59f9235c717383d2cd; 1d17de9534cb5a4c4c380d174cc2f9281b34f89e <77933e22adfe813be2bd10be08d6e950103c3967

The versions shown are the advisory's own. Patchlage compares no version numbers and derives no judgement from them — which version is installed is something a person has to look up.

Carried in the product catalogue

An estate covering these products can be recorded in Patchlage. An advisory about them appears in the next morning's situation report.

• Linux — Linux

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