CVE-2026-64531 — net: openvswitch: reject oversized nested action attrs
In the Linux kernel, the following vulnerability has been resolved: net: openvswitch: reject oversized nested action attrs Open vSwitch stores generated flow actions as nlattrs, whose nla_len field is u16. Commit a1e64addf3ff ("net: openvswitch: remove misbehaving actions length check") allowed the total sw_flow_actions stream to grow beyond 64 KiB, which is valid, but also removed the last guard preventing a generated nested action attribute from exceeding U16_MAX. An oversized generated container can thus be closed with a truncated nla_len. A later dump or teardown then walks a structurally different stream than the one that was validated. In particular, an oversized nested CLONE/CT action may cause subsequent bytes in the generated stream to be interpreted as independent actions. Keep the larger total-action-stream behavior, but make nested action close reject generated containers that do not fit in nla_len, and return the error through all callers. For recursive SAMPLE, CLONE, DEC_TTL, and CHECK_PKT_LEN builders, trim resource-owning action-list tails in reverse construction order before discarding failed wrappers, so resources copied into the rejected tails are released before the wrappers are removed. Most failed outer wrappers are discarded by truncating actions_len after child resources have been released. CHECK_PKT_LEN also trims its parent after branch resources are gone. SET/TUNNEL close failures unwind their known tun_dst ownership directly, and SET_TO_MASKED has no external ownership and truncates on close failure.
Who exploits it and how urgent it is
A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.
How the score was calculated
- Technical severity (high)+6
The score orders the patch queue; it does not replace your asset context (internet exposure, criticality, compensating controls).
Triage
Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.
Remediation
Fixes and mitigations documented by the sources — linked to the original advisory.
No fix documented by the sources we poll. That does not mean none exists: check the vendor advisory.
First 24 hours
Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.
- Identify exposed assets running the affected vendor/product/version combinations (Linux Linux).
- No fix documented in the sources: reduce exposure and monitor the vendor advisory.
- Search available logs for exploit probes, errors and authentication anomalies.
Affected scope
Vendor, product and versions as the sources word them.
| Vendor | Product | Versions | Status | Source |
|---|---|---|---|---|
| Linux | Linux |
≥ 057dbc5b72e9fcac439cd561c3a539b8a0edeb92 and < ab855641241387db062a5e41d9ad6b8561542572≥ 2532adbfe917c0e71dba2650ffc6efe396314c87 and < c66bd2626c2764f23764ff0f8277f44a9cfe8349≥ 4b1a0ee6164c7204c68ab5a9c48c07bfe8852485 and < d573250d228401f707f4dbc09d11227a6215ee5f≥ e6610f9c08b4c04cf7949c10fc246c071d00e935 and < f1efff8858403191361a01269c6fe8dd7f55a385≥ a1e64addf3ff9257b45b78bc7d743781c3f41340 and < dbd14f736be02cfe73049bd801af89becd1a0749≥ a1e64addf3ff9257b45b78bc7d743781c3f41340 and < 1b41cbe05b184f8861712f0806cc0c4f5d8c6dfe≥ a1e64addf3ff9257b45b78bc7d743781c3f41340 and < 3f1f755366687d051174739fb99f7d560202f60bversion 6b099d285d7ed324494b6d684f377aa103856118 and 6 more≥ 5.15.180 and < 5.15.212≥ 6.1.132 and < 6.1.178≥ 6.6.84 and < 6.6.145≥ 6.12.20 and < 6.12.97≥ 6.13.8 and < 6.14version 6.14 |
Vulnerable | CVE Program (cve.org) e CISA ADP |
Attack characteristics
The CVSS vector, decoded. It describes the attack, not your exposure to it.
Every base score collected
Sources score independently and may disagree; each row says who scored it and under which version.
| Score | Version | Severity | Expl. | Impact | Scored by |
|---|---|---|---|---|---|
| 7.8 | CVSS 3.1 | High | 1.8 | 5.9 | 416baaa9-dc9f-4396-8d5f-8c081fb06d67 via NIST National Vulnerability Database |
| 7.8 | CVSS 3.1 | High | — | — | Linux via CVE Program (cve.org) e CISA ADP |
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H (score shown at the top: 416baaa9-dc9f-4396-8d5f-8c081fb06d67) Detection
Read off the CVSS vector and the weakness class. Starting points, not tested rules.
- Local/physical vector: focus on endpoint telemetry (EDR) from affected hosts.
Timeline
What happened to this CVE, newest first.
- 2026
- Affected products added · linux/linux
- Record published
- CVSS changed · 7.8
- Source status changed · → Received
- Record created in this database
- CVE published
Source activity
Repeated readings are counted rather than listed.
- 1× Official description updated · Oct 15, 2026 – Oct 15, 2026
References
12 on the record
- git.kernel.org/stable/c/c66bd2626c2764f23764ff0f8277f44a9cfe8349
- www.openwall.com/lists/oss-security/2026/08/01/3
- www.openwall.com/lists/oss-security/2026/08/01/1
- git.kernel.org/stable/c/d573250d228401f707f4dbc09d11227a6215ee5f
- www.openwall.com/lists/oss-security/2026/07/31/17
- git.kernel.org/stable/c/1b41cbe05b184f8861712f0806cc0c4f5d8c6dfe
- git.kernel.org/stable/c/3f1f755366687d051174739fb99f7d560202f60b
- www.openwall.com/lists/oss-security/2026/07/28/8
- www.openwall.com/lists/oss-security/2026/08/22/1
- git.kernel.org/stable/c/ab855641241387db062a5e41d9ad6b8561542572
- git.kernel.org/stable/c/f1efff8858403191361a01269c6fe8dd7f55a385
- git.kernel.org/stable/c/dbd14f736be02cfe73049bd801af89becd1a0749
Elsewhere on this site
Related CVEs (same products)
- Critical CVE-2026-99999 ipv4: validate checksum_start before completing checksum 13h
- Unknown CVE-2026-98432 ipv4: free inet_opt and ireq_opt after an RCU grace period 13h
- Unknown CVE-2026-98424 wifi: cfg80211: undo netns switch if renaming the wiphy fails 1d
- Unknown CVE-2026-98425 wifi: mac80211: don't warn when an IBSS has no channel to scan 1d
- Unknown CVE-2026-98426 wifi: mwifiex: fix IRQ leak using wrong index in MSI-X error path 1d
- Unknown CVE-2026-98427 net/sched: codel: bound the dropping loop per dequeue call 1d
Not in any source we poll
Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.
- No FIRST EPSS score.
- No fixed version, patch or mitigation documented.
- No CISA SSVC assessment.
- No CWE classification.
- No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
- No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
- No exploit packet captures, log samples, or incident case IDs supplied.
Answered from this record
Text assembled only from the fields above — no additional claims.
What should defenders know first?
CVE-2026-64531 is "net: openvswitch: reject oversized nested action attrs", rated High. It affects Linux (Linux); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. CVSS 7.8 describes technical severity. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.
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