CVE-2026-23111 — netfilter: nf_tables: fix inverted genmask check in nft_map_catchall_activate()
In the Linux kernel, the following vulnerability has been resolved: netfilter: nf_tables: fix inverted genmask check in nft_map_catchall_activate() nft_map_catchall_activate() has an inverted element activity check compared to its non-catchall counterpart nft_mapelem_activate() and compared to what is logically required. nft_map_catchall_activate() is called from the abort path to re-activate catchall map elements that were deactivated during a failed transaction. It should skip elements that are already active (they don't need re-activation) and process elements that are inactive (they need to be restored). Instead, the current code does the opposite: it skips inactive elements and processes active ones. Compare the non-catchall activate callback, which is correct: nft_mapelem_activate(): if (nft_set_elem_active(ext, iter->genmask)) return 0; /* skip active, process inactive */ With the buggy catchall version: nft_map_catchall_activate(): if (!nft_set_elem_active(ext, genmask)) continue; /* skip inactive, process active */ The consequence is that when a DELSET operation is aborted, nft_setelem_data_activate() is never called for the catchall element. For NFT_GOTO verdict elements, this means nft_data_hold() is never called to restore the chain->use reference count. Each abort cycle permanently decrements chain->use. Once chain->use reaches zero, DELCHAIN succeeds and frees the chain while catchall verdict elements still reference it, resulting in a use-after-free. This is exploitable for local privilege escalation from an unprivileged user via user namespaces + nftables on distributions that enable CONFIG_USER_NS and CONFIG_NF_TABLES. Fix by removing the negation so the check matches nft_mapelem_activate(): skip active elements, process inactive ones.
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
- EPSS 0.5% (30-day exploitation probability)+6
- 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.
CISA SSVC assessment CISA
Three decision points CISA publishes for the CVEs it assesses (SSVC 2.0.3). A stakeholder decision, not a severity score.
Remediation
Fixes and mitigations documented by the sources — linked to the original advisory.
- Documented patch — git.kernel.org (NIST National Vulnerability Database)
- Documented patch — git.kernel.org (NIST National Vulnerability Database)
- Documented patch — git.kernel.org (NIST National Vulnerability Database)
- Documented patch — git.kernel.org (NIST National Vulnerability Database)
- Documented patch — git.kernel.org (NIST National Vulnerability Database)
- Documented patch — git.kernel.org (NIST National Vulnerability Database)
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, Linux Linux Kernel).
- Apply the fixed version or the patch documented under Remediation.
- Search available logs for exploit probes matching the vulnerability class (memory corruption), errors and authentication anomalies.
Affected scope
Vendor, product and versions as the sources word them.
| Vendor | Product | Versions | Status | Source |
|---|---|---|---|---|
| Linux | Linux |
version a136b7942ad2a50de708f76ea299ccb45ac7a7f9≥ 25aa2ad37c2162be1c0bc4fe6397f7e4c13f00f8 and < 8c760ba4e36c750379d13569f23f5a6e185333f5≥ d60be2da67d172aecf866302c91ea11533eca4d9 and < b9b6573421de51829f7ec1cce76d85f5f6fbbd7f≥ 628bd3e49cba1c066228e23d71a852c23e26da73 and < 42c574c1504aa089a0a142e4c13859327570473d≥ 628bd3e49cba1c066228e23d71a852c23e26da73 and < 1444ff890b4653add12f734ffeffc173d42862dd≥ 628bd3e49cba1c066228e23d71a852c23e26da73 and < 8b68a45f9722f2babe9e7bad00aa74638addf081≥ 628bd3e49cba1c066228e23d71a852c23e26da73 and < f41c5d151078c5348271ffaf8e7410d96f2d82f8version bc9f791d2593f17e39f87c6e2b3a36549a3705b1 and 9 moreversion 3c7ec098e3b588434a8b07ea9b5b36f04cef1f50version dc7cdf8cbcbf8b13de1df93f356ec04cdeef5c41≥ 5.15.121 and < 5.15.200≥ 6.1.36 and < 6.1.163≥ 4.19.316 and < 4.20≥ 5.4.262 and < 5.5≥ 5.10.188 and < 5.11≥ 6.3.10 and < 6.4version 6.4 |
Vulnerable | CVE Program (cve.org) e CISA ADP |
| Linux | Linux Kernel |
version 6.19-rc8version 6.4≥ 5.4.262 and < 5.5≥ 5.10.188 and < 5.11≥ 5.15.121 and < 5.15.200≥ 6.1.36 and < 6.1.163≥ 6.3.10 and < 6.4≥ 6.4.1 and < 6.6.124 and 10 more≥ 6.7 and < 6.12.70≥ 6.13 and < 6.18.10≥ 4.19.316 and < 4.20version 6.19-rc1version 6.19-rc2version 6.19-rc3version 6.19-rc4version 6.19-rc5version 6.19-rc6version 6.19-rc7 |
Vulnerable | NIST National Vulnerability Database |
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 | 1.8 | 5.9 | nvd@nist.gov via NIST National Vulnerability Database |
| 7.8 | CVSS 3.1 | High | 1.8 | 5.9 | 0b0ca135-0b70-47e7-9f44-1890c2a1c46c via NIST National Vulnerability Database |
| 7.8 | CVSS 3.1 | High | — | — | GitHub, Inc. via GitHub Security Advisories |
| 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: nvd@nist.gov) Weakness MITRE
Weakness class according to MITRE’s CWE catalog.
EPSS over time FIRST
Oct 13, 2026 → Oct 14, 2026 · 2 reading(s) · max 0.52%
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.
- Correlate service crashes/restarts with inbound traffic; repeated crashes may indicate attempts.
Timeline
What happened to this CVE, newest first.
- 2026
- Affected products added · linux/linux
- SSVC assessment updated
- Record published
- Fix documented
- CVSS changed · 7.8
- Source status changed · → Modified
- Record created in this database
- CVE published
Source activity
Repeated readings are counted rather than listed.
- 2× References added · Oct 14, 2026 – Oct 14, 2026
- 1× Official description updated · Oct 13, 2026 – Oct 13, 2026
References
24 on the record
- git.kernel.org/stable/c/8c760ba4e36c750379d13569f23f5a6e185333f5
- git.kernel.org/stable/c/8b68a45f9722f2babe9e7bad00aa74638addf081
- git.kernel.org/stable/c/f41c5d151078c5348271ffaf8e7410d96f2d82f8
- git.kernel.org/stable/c/b9b6573421de51829f7ec1cce76d85f5f6fbbd7f
- git.kernel.org/stable/c/1444ff890b4653add12f734ffeffc173d42862dd
- git.kernel.org/stable/c/42c574c1504aa089a0a142e4c13859327570473d
- cert-portal.siemens.com/productcert/html/ssa-457936.html
- github.com/advisories/GHSA-jh9m-9mr6-3ghc
- cert-portal.siemens.com/productcert/html/ssa-253495.html
- access.redhat.com/errata/RHSA-2026:18134
- access.redhat.com/errata/RHSA-2026:9112
- cert-portal.siemens.com/productcert/html/ssa-019113.html
- security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-23111.json
- access.redhat.com/errata/RHSA-2026:62639
- access.redhat.com/errata/RHSA-2026:62641
- access.redhat.com/errata/RHSA-2026:10996
- access.redhat.com/security/cve/CVE-2026-23111
- nvd.nist.gov/vuln/detail/CVE-2026-23111
- cert-portal.siemens.com/productcert/html/ssa-082556.html
- access.redhat.com/errata/RHSA-2026:6570
- bugzilla.redhat.com/show_bug.cgi
- blog.exodusintel.com/2026/06/08/off-by-exploiting-a-use-after-free-in-the-linux-kernel/
- access.redhat.com/errata/RHSA-2026:10108
- blog.exodusintel.com/2026/06/08/off-by-exploiting-a-use-after-free-in-the-linux-kernel
Elsewhere on this site
Related CVEs (same products)
- Critical CVE-2026-99999 ipv4: validate checksum_start before completing checksum 9h
- Unknown CVE-2026-98432 ipv4: free inet_opt and ireq_opt after an RCU grace period 9h
- 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 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-2026-23111 is "netfilter: nf_tables: fix inverted genmask check in nft_map_catchall_activate()", 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. EPSS 0.52% estimates the probability of exploitation in 30 days; neither replaces your asset context. 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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