---
id: CVE-2026-68160
title: 'ceph: fix pre-auth out-of-bounds read on snaptrace in ceph_handle_caps()'
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  ceph: fix pre-auth out-of-bounds read on snaptrace in ceph_handle_caps()

  ceph_handle_caps() reads snap_trace_len from the wire-format
  ceph_mds_caps header and uses it …
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
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= a8599bd821d084d04a3290fffae1071624ec00ea <
    f913192fc782288e060dafc329b2346934be34cc
  - >-
    Linux >= a8599bd821d084d04a3290fffae1071624ec00ea <
    0c011137194036424e974677e0f1592e22a33d8c
  - >-
    Linux >= a8599bd821d084d04a3290fffae1071624ec00ea <
    cc93f68a31c9b831abf2db8647b5f5b10329d793
  - >-
    Linux >= a8599bd821d084d04a3290fffae1071624ec00ea <
    9081c71796724ffe96cba253f68fbe42363c5295
  - >-
    Linux >= a8599bd821d084d04a3290fffae1071624ec00ea <
    03b417afce19ee6b6e61f1bbbbebac924c9f36d1
  - >-
    Linux >= a8599bd821d084d04a3290fffae1071624ec00ea <
    a4228b93706fb74a484e6ffb271c1cc2af3a2ddb
  - >-
    Linux >= a8599bd821d084d04a3290fffae1071624ec00ea <
    71893c342a26bcff92eaab0b2b75d64aed19308a
  - >-
    Linux >= a8599bd821d084d04a3290fffae1071624ec00ea <
    4dbc71bcaf9a30abf3920a4e2cc4ed33bba78c02
  - Linux 2.6.34
ssvc:
  exploitation: none
  automatable: 'yes'
  technicalImpact: total
  timestamp: '2026-10-16T15:45:20.340785Z'
published: '2026-08-10'
updated: '2026-10-16'
sourceUpdated: '2026-10-16T15:53:01.677Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-68160'
references:
  - url: 'https://git.kernel.org/stable/c/f913192fc782288e060dafc329b2346934be34cc'
  - url: 'https://git.kernel.org/stable/c/0c011137194036424e974677e0f1592e22a33d8c'
  - url: 'https://git.kernel.org/stable/c/cc93f68a31c9b831abf2db8647b5f5b10329d793'
  - url: 'https://git.kernel.org/stable/c/9081c71796724ffe96cba253f68fbe42363c5295'
  - url: 'https://git.kernel.org/stable/c/03b417afce19ee6b6e61f1bbbbebac924c9f36d1'
  - url: 'https://git.kernel.org/stable/c/a4228b93706fb74a484e6ffb271c1cc2af3a2ddb'
  - url: 'https://git.kernel.org/stable/c/71893c342a26bcff92eaab0b2b75d64aed19308a'
  - url: 'https://git.kernel.org/stable/c/4dbc71bcaf9a30abf3920a4e2cc4ed33bba78c02'
tags:
  - cve.org
epss: 0.00772
epssPercentile: 0.54802
ingestedAt: '2026-10-16T17:24:46.846Z'
---

## Overview

In the Linux kernel, the following vulnerability has been resolved:

ceph: fix pre-auth out-of-bounds read on snaptrace in ceph_handle_caps()

ceph_handle_caps() reads snap_trace_len from the wire-format
ceph_mds_caps header and uses it unconditionally to build a fake
end pointer (snaptrace + snaptrace_len) that is later handed to
ceph_update_snap_trace() in the CEPH_CAP_OP_IMPORT case:

    snaptrace     = h + 1;
    snaptrace_len = le32_to_cpu(h->snap_trace_len);
    p             = snaptrace + snaptrace_len;
    ...
    case CEPH_CAP_OP_IMPORT:
        if (snaptrace_len) {
            ...
            if (ceph_update_snap_trace(mdsc, snaptrace,
                                       snaptrace + snaptrace_len,
                                       false, &realm)) { ... }

ceph_update_snap_trace() then decodes a struct ceph_mds_snap_realm
from snaptrace using ceph_decode_need(&p, e, sizeof(*ri), bad)
with the attacker-supplied fake end e == snaptrace + snaptrace_len.
With snaptrace_len == 0xFFFFFFFF the bound check is trivially
satisfied, ri = p reads sizeof(struct ceph_mds_snap_realm) past
the legitimate msg->front buffer, and ri->num_snaps /
ri->num_prior_parent_snaps then drive further out-of-bounds
reads of the encoded snap arrays.

The eleven msg_version >= 2 .. msg_version >= 12 decoder blocks
above the op switch each catch this OOB through their
ceph_decode_*_safe() / ceph_decode_need() helpers, but they sit
behind a hdr.version-gated if, so a malicious or compromised
MDS that sets msg->hdr.version = 1 reaches the IMPORT path with
no version-gated decoder having validated snap_trace_len. The
shape has been present since ceph_handle_caps() was introduced.

Validate snap_trace_len against the message front buffer before
consuming it, using the canonical ceph_decode_need() / ceph_has_room()
helper.  The helper bounds the length with subtraction (n <= end - p,
guarded by end >= p) rather than pointer addition, so it is wrap-safe
for the attacker-controlled u32 length on 32-bit builds where
p + snap_trace_len could overflow the address space.  This matches the
rest of the ceph decode path (e.g. the pool_ns_len check a few lines
below), and the existing goto bad cleanup already covers this exit
path.

## Affected

- `Linux >= a8599bd821d084d04a3290fffae1071624ec00ea < f913192fc782288e060dafc329b2346934be34cc`
- `Linux >= a8599bd821d084d04a3290fffae1071624ec00ea < 0c011137194036424e974677e0f1592e22a33d8c`
- `Linux >= a8599bd821d084d04a3290fffae1071624ec00ea < cc93f68a31c9b831abf2db8647b5f5b10329d793`
- `Linux >= a8599bd821d084d04a3290fffae1071624ec00ea < 9081c71796724ffe96cba253f68fbe42363c5295`
- `Linux >= a8599bd821d084d04a3290fffae1071624ec00ea < 03b417afce19ee6b6e61f1bbbbebac924c9f36d1`
- `Linux >= a8599bd821d084d04a3290fffae1071624ec00ea < a4228b93706fb74a484e6ffb271c1cc2af3a2ddb`
- `Linux >= a8599bd821d084d04a3290fffae1071624ec00ea < 71893c342a26bcff92eaab0b2b75d64aed19308a`
- `Linux >= a8599bd821d084d04a3290fffae1071624ec00ea < 4dbc71bcaf9a30abf3920a4e2cc4ed33bba78c02`
- `Linux 2.6.34`

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.