CVE-2026-89651: ceph: bound MDSCapAuth path and fs_name decode in handle_session()
- Is it exploited?
Not on CISA's list. CISA has not added it to the Known Exploited Vulnerabilities catalog as of . If CISA adds it, this page shows it as known exploited.
- How likely is exploitation in the next 30 days?
- 0.6%
EPSS score, percentile 50.3 of all scored records. A probability estimated by FIRST, not a report of exploitation.
- How severe?
- 9.8 Critical
CVSS v3.1 base score, given by the CNA
- What should I do?
CISA has set no required action, because the vulnerability is not in KEV.
The CVE record links no vendor advisory, patch or mitigation.
- Which versions are affected?
Affected
- 6.10
Unaffected before 6.10; 6.12.109; 6.18.50; 7.2.4; 7.3
Source: CISA KEV 2026.10.29, as of ; FIRST EPSS, as of ; CVE List, as of . About the data.
What to do
Advisories and patches
The CVE record links no vendor advisory, patch or mitigation.
This summary is based on the CVE record as of . Check the vendor's advisory before you act: affected versions and fixes can change.
Affected products and versions
As listed in the CVE record.
| Status | Versions |
|---|---|
| Affected | from 1d17de9534cb to before dc5c7dffda92 |
| Affected | from 1d17de9534cb to before c37db86d2b5e |
| Affected | from 1d17de9534cb to before 5f892c767b30 |
| Affected | from 1d17de9534cb to before 77933e22adfe |
Versions not listed are: unaffected.
| Status | Versions |
|---|---|
| Affected | 6.10 |
| Unaffected | before 6.10 |
| Unaffected | 6.12.109 |
| Unaffected | 6.18.50 |
| Unaffected | 7.2.4 |
| Unaffected | 7.3 |
Versions not listed are: affected.
Versions the record lists as unaffected: 6.12.109, 6.18.50, 7.2.4, 7.3.
Source: CVE List, as of . About the data.
About this vulnerability
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 cep…
Summary: CVE record, as of .
- CISA has not added CVE-2026-89651 to its Known Exploited Vulnerabilities (KEV) catalog, as of 29 Oct 2026.
- The CVE record was published on 11 Sep 2026.
- The CVE record carries a CVSS v3.1 base score of 9.8 (Critical), given by its CNA.
- FIRST's EPSS model puts the probability of exploitation in the next 30 days at 0.6% (percentile 50.3), as of 29 Oct 2026. EPSS is a statistical estimate, not a report of exploitation.
Source: CISA KEV 2026.10.29, as of ; CVE List, as of ; FIRST EPSS, as of . About the data.
Description
ceph: bound MDSCapAuth path and fs_name decode in handle_session()
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: CVE List, as of . About the data.
Timeline
| Date | Event |
|---|---|
| CVE record published | |
| CVE record last updated |
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