In the Linux kernel, the following vulnerability has been resolved:
smb: client: fix use-after-free in cifs_oplock_break
A race condition can occur in cifs_oplock_break() leading to a
use-after-free of the cinode structure when unmounting:
cifs_oplock_break()
_cifsFileInfo_put(cfile)
cifsFileInfo_put_final()
cifs_sb_deactive()
[last ref, start releasing sb]
kill_sb()
kill_anon_super()
generic_shutdown_super()
evict_inodes()
dispose_list()
evict()
destroy_inode()
call_rcu(&inode->i_rcu, i_callback)
spin_lock(&cinode->open_file_lock) <- OK
[later] i_callback()
cifs_free_inode()
kmem_cache_free(cinode)
spin_unlock(&cinode->open_file_lock) <- UAF
cifs_done_oplock_break(cinode) <- UAF
The issue occurs when umount has already released its reference to the
superblock. When _cifsFileInfo_put() calls cifs_sb_deactive(), this
releases the last reference, triggering the immediate cleanup of all
inodes under RCU. However, cifs_oplock_break() continues to access the
cinode after this point, resulting in use-after-free.
Fix this by holding an extra reference to the superblock during the
entire oplock break operation. This ensures that the superblock and
its inodes remain valid until the oplock break completes.
What the EG score is made of (scorer v4.0: the three questions the 0–10 score mixes, published apart · methodology)
The EG score (7.8): severity, escalated by confirmed exploitation. This CVE's 7.8 is its impact severity (EG Severity), not escalated.
- EG Severity
- 7.8 HIGHCVSS-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 2026-10-29). 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, and whom BOD 26-04 binds: 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.
The score's inputs: 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