In the Linux kernel, the following vulnerability has been resolved:
libceph: fix two unsafe bare decodes in decode_lockers()
decode_lockers() in cls_lock_client.c contains two bare decode operations
that allow a malicious or compromised OSD to trigger slab-out-of-bounds
reads:
- ceph_decode_32(p) at the num_lockers field has no preceding bounds
check. ceph_start_decoding() accepts struct_len=0 as valid -- the
internal ceph_decode_need(p, end, 0, bad) always passes -- so when an
OSD sends struct_len=0, ceph_start_decoding() returns success with
p == end. The immediately following bare ceph_decode_32(p) then reads
4 bytes past the validated buffer boundary. The garbage value is
passed directly to kzalloc_objs() as the locker count.
The sibling function decode_watchers() in osd_client.c already uses
ceph_decode_32_safe() after its own ceph_start_decoding() call.
decode_lockers() was the only site using the bare variant.
- ceph_decode_8(p) after the decode_locker() loop has no preceding
bounds check. If an OSD crafts num_lockers such that the loop
advances p exactly to end, the subsequent bare ceph_decode_8(p) reads
one byte past the validated buffer boundary. The result is passed
directly into *type, which is used as a lock type discriminator by
callers, giving an OSD-controlled one-byte OOB read with direct
influence over the lock type field.
Fix both by replacing bare operations with their safe variants:
ceph_decode_32(p) -> ceph_decode_32_safe(p, end, *num_lockers,
err_inval)
ceph_decode_8(p) -> ceph_decode_8_safe(p, end, *type,
err_free_lockers)
The goto targets differ intentionally:
err_inval: is a new label returning -EINVAL directly. It is used for
the pre-allocation failure path where *lockers is not yet allocated
and must not be passed to ceph_free_lockers().
err_free_lockers: is the existing label. It is used for the
post-allocation failure path where *lockers is allocated and must
be freed.
ret is set to -EINVAL before ceph_decode_8_safe() so that
err_free_lockers returns the correct error code on bounds violation.
Without this, err_free_lockers would return a stale ret value (0 from
the successful decode_locker() loop), silently swallowing the error.
-EINVAL is correct for both failure paths. The data received from the
OSD is structurally malformed. -ENOMEM would misrepresent the failure
class to callers and to stable@ backporters triaging error paths.
Attacker model: a malicious or compromised OSD in a multi-tenant Ceph
deployment can trigger this against any kernel client that issues the
lock.get_info class method (e.g. during RBD exclusive lock acquisition).
[ idryomov: trim changelog, formatting ]
What the EG score is made of (scorer v4.0: the three questions the 0–10 score mixes, published apart · methodology)
The EG score (9.8): severity, escalated by confirmed exploitation. This CVE's 9.8 is its impact severity (EG Severity), not escalated.
- EG Severity
- 9.8 CRITICALCVSS-B, impact only: no KEV listing, EPSS or EG-KEV tier raises it.GitHub Security Advisory CVSS
- EG Likelihood
- 0.4% within 30 daysSource: FIRST EPSS (model v2026.06.15, score date 2026-10-19). FIRST's exploitation probability, not an EchelonGraph model.
- Confirmed exploitation
- None on record (CISA KEV, EG-KEV Tier 1)Reported apart from the likelihood: an observed fact, not a probability.
- EG Priority
- SSVC Track at medium mission impactTrack at low or medium mission impact; Attend at high (mission-essential systems).CISA BOD 26-04: 3 days if the affected system is publicly exposed; 60 days if it is not.Each input and its source: the SSVC and BOD 26-04 blocks below.
SSVC (CISA's decision table, applied by EchelonGraph)Track at low or medium mission impact; Attend at high (mission-essential systems).
A fix is available. Apply it within your standard update timelines at low or medium mission impact and sooner than that at high.
Exploitation none (CISA Vulnrichment) · Automatable yes (CISA Vulnrichment) · Technical impact total (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE. Mission impact is CISA's Mission & Well-being decision point, and only you can judge it. CISA's table makes it high when Mission Prevalence is Essential — the vulnerable component "directly provides capabilities that constitute at least one MEF for at least one entity" (MEF: mission essential function) — or when Public Well-Being Impact is Irreversible: "multiple fatalities are likely", the cyber-physical system "is likely lost or destroyed", "extreme or serious externalities" are imposed on other parties, or social systems such as elections or the financial grid "are destabilized and potentially collapse". CISA's decision table
BOD 26-04 (CISA's remediation timeline, Table 1)3 days if the affected system is publicly exposed; 60 days if it is not.
In CISA KEV no (CISA's KEV catalog) · Automatable yes (CISA Vulnrichment) · Technical impact total (CISA Vulnrichment). Whether your system is publicly exposed is yours to answer. BOD 26-04 binds US Federal Civilian Executive Branch agencies; for anyone else it is CISA's published timeline, a reference rather than an obligation. The directive · how EchelonGraph applies it