CVE-2026-89649ceph: bound xattr value length in __build_xattrs()

Description

In the Linux kernel, the following vulnerability has been resolved: ceph: bound xattr value length in __build_xattrs() __build_xattrs() decodes the MDS-supplied xattr blob one attribute at a time. For each attribute it reads a 32-bit name length, advances past the name bytes, reads a 32-bit value length, records the value pointer, and advances past the value bytes. The two length fields are read with ceph_decode_32_safe(), but the value bytes themselves are advanced over with a bare "p += len" and no ceph_decode_need() check that "len" bytes remain in the blob. For every attribute except the last, the next iteration's ceph_decode_32_safe() on the following name length implicitly verifies that the previous value did not run past the blob end. The final attribute has no successor, so its decoded value length is never checked against the blob bounds. A malicious or compromised metadata server can set the last attribute's value length larger than the bytes actually present in the blob. The blob is a dedicated kvmalloc() allocation sized to the wire length (ceph_buffer_new() in ceph_fill_inode()). __set_xattr() records the oversized length in xattr->val_len verbatim, and a later getxattr(2) runs memcpy(value, xattr->val, xattr->val_len) into a user-supplied buffer, copying bytes past the end of the allocation back to user space. Impact: a malicious metadata server discloses adjacent kernel heap bytes to a local user via getxattr(2) on a CephFS file. Add the missing ceph_decode_need() so an out-of-bounds value length on the final attribute fails the decode and returns -EIO instead of being stored.

Timeline

Scores

EPSS (exploitation in 30 days)

0.68% · top 47% of all CVEs (14 Nov 2026)

CISA SSVC

Exploitation: none · Automatable: yes · Technical impact: partial

The list uses the assigner's score when there is one, then CISA's, then NVD's: Critical 9.1.

Affected products

• Linux · Linux

  • affected 355da1eb7a1f91c276b991764e951bbcd8047599 – < 848b80ca6b410f350d08b8ac19a00ef88223f2ea
  • affected 355da1eb7a1f91c276b991764e951bbcd8047599 – < 01e3f19c301d492e12f16b3b463ac14d7cf3ebe7
  • affected 355da1eb7a1f91c276b991764e951bbcd8047599 – < cb0cd79ae80476d1bc06bd9678484b6736f19588
  • affected 355da1eb7a1f91c276b991764e951bbcd8047599 – < 61f085cb8976c9cebc90e1a8933e4cc1ad8b0fce
  • affected 355da1eb7a1f91c276b991764e951bbcd8047599 – < 38be2f3c41ecaba58bb92dc16603e09ba9fd64f1
  • affected 355da1eb7a1f91c276b991764e951bbcd8047599 – < 1dd356310b1660215f9a3626580bf8b363ef981e
  • affected 355da1eb7a1f91c276b991764e951bbcd8047599 – < b12b3320c81fd72ab36388fb2445fec9c3038f10
  • affected 355da1eb7a1f91c276b991764e951bbcd8047599 – < 68d541754d6cd3bb98d1fd8314f57e5eb533557d

• Linux · Linux

  • affected 2.6.34
  • unaffected < 2.6.34
  • unaffected 5.10.270 – ≤ 5.10.*
  • unaffected 5.15.221 – ≤ 5.15.*
  • unaffected 6.1.188 – ≤ 6.1.*
  • unaffected 6.6.157 – ≤ 6.6.*
  • unaffected 6.12.109 – ≤ 6.12.*
  • unaffected 6.18.50 – ≤ 6.18.*
  • unaffected 7.2.4 – ≤ 7.2.*
  • unaffected 7.3 – ≤ *

Sources

The same CVE in the primary databases and aggregators, to check against.

• CVE.org record (opens in a new tab)
• CVE List JSON (GitHub) (opens in a new tab)
• NVD (opens in a new tab)
• FIRST EPSS (opens in a new tab)
• EUVD EUVD-2026-76561 (opens in a new tab)
• OSV.dev (opens in a new tab)
• GitHub Advisories (opens in a new tab)
• CIRCL Vulnerability-Lookup (opens in a new tab)

Badge for a README or a ticket

[![CVE-2026-89649](https://cveledger.app/badge/CVE-2026-89649.svg)](https://cveledger.app/cve/CVE-2026-89649)

Record last updated 19 Oct 2026, 08:50 UTC.