In the Linux kernel, the following vulnerability has been resolved:
netfilter: nft_set_pipapo_avx2: don't return non-matching entry on expiry
New test case fails unexpectedly when avx2 matching functions are used.
The test first loads a ranomly generated pipapo set
with 'ipv4 . port' key, i.e. nft -f foo.
This works. Then, it reloads the set after a flush:
(echo flush set t s; cat foo) | nft -f -
This is expected to work, because its the same set after all and it was
already loaded once.
But with avx2, this fails: nft reports a clashing element.
The reported clash is of following form:
We successfully re-inserted
a . b
c . d
Then we try to insert a . d
avx2 finds the already existing a . d, which (due to 'flush set') is marked
as invalid in the new generation. It skips the element and moves to next.
Due to incorrect masking, the skip-step finds the next matching
element *only considering the first field*,
i.e. we return the already reinserted "a . b", even though the
last field is different and the entry should not have been matched.
No such error is reported for the generic c implementation (no avx2) or when
the last field has to use the 'nft_pipapo_avx2_lookup_slow' fallback.
Bisection points to
7711f4bb4b36 ("netfilter: nft_set_pipapo: fix range overlap detection")
but that fix merely uncovers this bug.
Before this commit, the wrong element is returned, but erronously
reported as a full, identical duplicate.
The root-cause is too early return in the avx2 match functions.
When we process the last field, we should continue to process data
until the entire input size has been consumed to make sure no stale
bits remain in the map.
What the EG score is made of (scorer v4.0: the three questions the 0–10 score mixes, published apart · methodology)
The EG score (9.4): severity, escalated by confirmed exploitation. This CVE's 9.4 is its impact severity (EG Severity), not escalated.
- EG Severity
- 9.4 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 2026-10-28). 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