In the Linux kernel, the following vulnerability has been resolved:
btrfs: fix use-after-free after failure to create a snapshot
At ioctl.c:create_snapshot(), we allocate a pending snapshot structure and
then attach it to the transaction's list of pending snapshots. After that
we call btrfs_commit_transaction(), and if that returns an error we jump
to 'fail' label, where we kfree() the pending snapshot structure. This can
result in a later use-after-free of the pending snapshot:
1) We allocated the pending snapshot and added it to the transaction's
list of pending snapshots;
2) We call btrfs_commit_transaction(), and it fails either at the first
call to btrfs_run_delayed_refs() or btrfs_start_dirty_block_groups().
In both cases, we don't abort the transaction and we release our
transaction handle. We jump to the 'fail' label and free the pending
snapshot structure. We return with the pending snapshot still in the
transaction's list;
3) Another task commits the transaction. This time there's no error at
all, and then during the transaction commit it accesses a pointer
to the pending snapshot structure that the snapshot creation task
has already freed, resulting in a user-after-free.
This issue could actually be detected by smatch, which produced the
following warning:
fs/btrfs/ioctl.c:843 create_snapshot() warn: '&pending_snapshot->list' not removed from list
So fix this by not having the snapshot creation ioctl directly add the
pending snapshot to the transaction's list. Instead add the pending
snapshot to the transaction handle, and then at btrfs_commit_transaction()
we add the snapshot to the list only when we can guarantee that any error
returned after that point will result in a transaction abort, in which
case the ioctl code can safely free the pending snapshot and no one can
access it anymore.
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
- 0.2% within 30 daysSource: FIRST EPSS (model v2026.06.15, score date 2026-10-27). 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 every mission impact level.CISA BOD 26-04: 60 days if the affected system is publicly exposed; Fix on system upgrade 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 every mission impact level.
A fix is available. Apply it within your standard update timelines.
Exploitation none (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact partial (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)60 days if the affected system is publicly exposed; Fix on system upgrade if it is not.
The score's inputs: In CISA KEV no (CISA's KEV catalog) · Automatable no (CISA Vulnrichment) · Technical impact partial (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