In the Linux kernel, the following vulnerability has been resolved:
mm: swap_cgroup: fix NULL deref in lookup_swap_cgroup_id on swapless host
lookup_swap_cgroup_id() passes swap_cgroup_ctrl[type].map to
__swap_cgroup_id_lookup() without checking that the type was ever
registered via swap_cgroup_swapon(). On a swapless host every ctrl->map
is NULL, so __swap_cgroup_id_lookup() dereferences NULL + a scaled
swp_offset().
Since commit bea67dcc5eea ("mm: attempt to batch free swap entries for
zap_pte_range()"), zap_pte_range() -> swap_pte_batch() calls
lookup_swap_cgroup_id() on any non-present, non-none PTE that decodes as a
real swap entry, without first validating it against swap_info[]. A
single PTE corrupted into a type-0 swap entry takes the host down at
process exit.
We hit this in production on a swapless 6.12.58 host: ~1s of
"get_swap_device: Bad swap file entry 3f800204222bb" (do_swap_page() being
correctly defensive about the same entry) followed by
BUG: unable to handle page fault for address: 000003f800204220
RIP: 0010:lookup_swap_cgroup_id+0x2b/0x60
Call Trace:
swap_pte_batch+0xbf/0x230
zap_pte_range+0x4c8/0x780
unmap_page_range+0x190/0x3e0
exit_mmap+0xd9/0x3c0
do_exit+0x20c/0x4b0
syzbot has reported the identical stack.
The source of the PTE corruption is a separate bug; this change makes the
teardown path as robust as the fault path already is. Every other caller
of lookup_swap_cgroup_id() is downstream of a get_swap_device() that has
already validated the entry, so the new branch is cold.
What the EG score is made of (scorer v4.0: the three questions the 0–10 score mixes, published apart · methodology)
The EG score (5.5): severity, escalated by confirmed exploitation. This CVE's 5.5 is its impact severity (EG Severity), not escalated.
- EG Severity
- 5.5 MEDIUMCVSS-B, impact only: no KEV listing, EPSS or EG-KEV tier raises it.GitHub Security Advisory CVSS
- EG Likelihood
- 0.1% within 30 daysSource: FIRST EPSS (model v2026.06.15, score date 2026-11-07). 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; Track* at high (mission-essential systems).CISA BOD 26-04: 14 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 low or medium mission impact; Track* at high (mission-essential systems).
A fix is available. Apply it within your standard update timelines.
Exploitation none (no CISA value, KEV listing or exploit code on record) · Automatable no (CISA's BOD 26-04 default) · Technical impact total (CISA's BOD 26-04 default). EchelonGraph holds no SSVC assessment of this CVE from CISA: none of these inputs is from 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)14 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's BOD 26-04 default) · Technical impact total (CISA's BOD 26-04 default). Where an input reads “CISA's BOD 26-04 default”, no one has published it for this CVE, and CISA's implementation guidance says: “If “Automatable” and “Technical Impact” information items about a CVE ID are not available and the CVE ID is not in the KEV Catalog, CISA will treat its values as “no” and “total,” respectively, until CISA or a third party provides metadata about the CVE ID. CISA will always provide the Vulnrichment data for a CVE ID listed in the KEV Catalog.” 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