CVE-2026-80557

Status: UPDATED  |  Advisory ID: CVE-2026-80557

Key Details

Affected Products, Subsystems & Sectors

What to Know

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

libceph: fix OOB read in decode_watchers() via missing bounds check

ceph_start_decoding() validates that struct_len bytes remain in the

buffer after the encoding header, but accepts struct_len=0 as valid:

ceph_decode_need(p, end, 0, bad) always passes. When a malicious or

compromised OSD sends an obj_list_watch_response_t reply with

struct_len=0, ceph_start_decoding() returns success with p == end,

leaving zero bytes guaranteed for subsequent reads.

The immediately following ceph_decode_32(p) in decode_watchers() has

no preceding bounds check. With p == end this is a 4-byte read past

the validated buffer boundary. The garbage value is then passed

directly to kzalloc_objs() as the watcher count.

The sibling function decode_watcher() already uses the safe variants

(ceph_decode_copy_safe, ceph_decode_64_safe, ceph_decode_skip_32)

after its own ceph_start_decoding() call. decode_watchers() is the

only site that uses the bare variant, confirming an oversight.

Fix by replacing ceph_decode_32(p) with ceph_decode_32_safe(p, end,

*num_watchers, bad), consistent with the established pattern.

Attacker model: a malicious or compromised OSD in a multi-tenant Ceph

deployment (e.g. cloud) can trigger this against any kernel client

that calls CEPH_OSD_OP_LIST_WATCHERS, without any further privileges

beyond OSD session establishment.

[ idryomov: trim changelog ] (NVD)

What to Do

Monitor Linux's web page for any future patch releases.

References