In the Linux kernel, the following vulnerability has been resolved:
mm: mglru: fix stale batch updates after memcg reparenting
The mglru page table walker batches per-generation size deltas in
walk->nr_pages while walking page tables without holding the lruvec lock.
The reset_batch_size() later folds those deltas into walk->lruvec under
the lruvec lock.
The page table walker can run concurrently with the memcg reparenting path
as follows:
CPU0 CPU1
==== ====
walk_mm
--> walk_page_range
--> update_batch_size
--> walk->nr_pages += delta
mem_cgroup_css_offline
--> memcg_reparent_objcgs
--> lock lruvec
lru_gen_reparent_memcg
--> reparent child folios to parent
unlock lruvec
lock lruvec
reset_batch_size
--> child lrugen->nr_pages += delta
This will trigger the following warning in lru_gen_exit_memcg():
VM_WARN_ON_ONCE(memchr_inv(lruvec->lrugen.nr_pages, 0,
sizeof(lruvec->lrugen.nr_pages)));
And the user-visible impact of underestimated nr_pages in MGLRU was
premature OOMs because MGLRU does not try to reclaim memory when nr_pages
reaches zero, but there are still more pages.
To fix it, make reset_batch_size() check CSS_DYING under RCU before
flushing the pending batch. A non-dying memcg keeps the original lruvec
stable against RCU-delayed offlining; a dying memcg redirects the deltas
to the first non-dying ancestor.
What the EG score is made of (scorer v4.0: the three questions the 0–10 score mixes, published apart · methodology)
- EG Severity
- Not assessed: no CVSS publishedA missing CVSS is not a severity of zero.
- EG Likelihood
- 0.2% 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
- No SSVC decision: EchelonGraph has not assessed this CVECISA 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: the BOD 26-04 block below.
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.
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