CVE-2025-38721 — netfilter: ctnetlink: fix refcount leak on table dump
In the Linux kernel, the following vulnerability has been resolved: netfilter: ctnetlink: fix refcount leak on table dump There is a reference count leak in ctnetlink_dump_table(): if (res < 0) { nf_conntrack_get(&ct->ct_general); // HERE cb->args[1] = (unsigned long)ct; ... While its very unlikely, its possible that ct == last. If this happens, then the refcount of ct was already incremented. This 2nd increment is never undone. This prevents the conntrack object from being released, which in turn keeps prevents cnet->count from dropping back to 0. This will then block the netns dismantle (or conntrack rmmod) as nf_conntrack_cleanup_net_list() will wait forever. This can be reproduced by running conntrack_resize.sh selftest in a loop. It takes ~20 minutes for me on a preemptible kernel on average before I see a runaway kworker spinning in nf_conntrack_cleanup_net_list. One fix would to change this to: if (res < 0) { if (ct != last) nf_conntrack_get(&ct->ct_general); But this reference counting isn't needed in the first place. We can just store a cookie value instead. A followup patch will do the same for ctnetlink_exp_dump_table, it looks to me as if this has the same problem and like ctnetlink_dump_table, we only need a 'skip hint', not the actual object so we can apply the same cookie strategy there as well.
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 0.2% (30-day exploitation probability)+1
- Technical severity (medium)+3
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.
- 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)
- 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 (Debian Debian Linux, Linux Linux, Linux Linux Kernel).
- Apply the fixed version or the patch documented under Remediation.
- 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 |
|---|---|---|---|---|
| Debian | Debian Linux | version 11.0 | Vulnerable | NIST National Vulnerability Database |
| Linux | Linux |
version 2.6.18≥ d205dc40798d97d63ad348bfaf7394f445d152d4 and < de788b2e6227462b6dcd0e07474e72c089008f74≥ d205dc40798d97d63ad348bfaf7394f445d152d4 and < a62d6aa3f31f216b637a4c71b7a8bfc7c57f049b≥ d205dc40798d97d63ad348bfaf7394f445d152d4 and < e14f72aa66c029db106921d621edcedef68e065b≥ d205dc40798d97d63ad348bfaf7394f445d152d4 and < a2cb4df7872de069f809de2f076ec8e54d649fe3≥ d205dc40798d97d63ad348bfaf7394f445d152d4 and < 30cf811058552b8cd0e98dff677ef3f89d6d34ce≥ d205dc40798d97d63ad348bfaf7394f445d152d4 and < 41462f4cfc583513833f87f9ee55d12da651a7e3≥ d205dc40798d97d63ad348bfaf7394f445d152d4 and < 19b909a4b1452fb97e477d2f08b97f8d04095619 and 2 more≥ d205dc40798d97d63ad348bfaf7394f445d152d4 and < 962518c6ca9f9a13df099cafa429f72f68ad61f0≥ d205dc40798d97d63ad348bfaf7394f445d152d4 and < 586892e341fbf698e7cbaca293e1353957db725a |
Vulnerable | CVE Program (cve.org) e CISA ADP |
| Linux | Linux Kernel |
version 2.6.18-rc7version 6.17-rc1version 2.6.18-rc6version 2.6.18-rc5version 2.6.18≥ 6.16 and < 6.16.2≥ 6.13 and < 6.15.11≥ 6.7 and < 6.12.43 and 5 more≥ 6.2 and < 6.6.103≥ 5.16 and < 6.1.149≥ 5.11 and < 5.15.190≥ 5.5 and < 5.10.241≥ 2.6.19 and < 5.4.297 |
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 |
|---|---|---|---|---|---|
| 5.5 | CVSS 3.1 | Medium | 1.8 | 3.6 | nvd@nist.gov via NIST National Vulnerability Database |
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H (score shown at the top: nvd@nist.gov) 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
- Fix documented
- CVSS changed · 5.5
- Source status changed · → Modified
- Record created in this database
- 2025
- CVE published
Source activity
Repeated readings are counted rather than listed.
- 1× Official description updated · Oct 15, 2026 – Oct 15, 2026
References
15 on the record
- git.kernel.org/stable/c/41462f4cfc583513833f87f9ee55d12da651a7e3
- git.kernel.org/stable/c/962518c6ca9f9a13df099cafa429f72f68ad61f0
- git.kernel.org/stable/c/a2cb4df7872de069f809de2f076ec8e54d649fe3
- git.kernel.org/stable/c/de788b2e6227462b6dcd0e07474e72c089008f74
- git.kernel.org/stable/c/30cf811058552b8cd0e98dff677ef3f89d6d34ce
- git.kernel.org/stable/c/e14f72aa66c029db106921d621edcedef68e065b
- git.kernel.org/stable/c/586892e341fbf698e7cbaca293e1353957db725a
- git.kernel.org/stable/c/19b909a4b1452fb97e477d2f08b97f8d04095619
- git.kernel.org/stable/c/a62d6aa3f31f216b637a4c71b7a8bfc7c57f049b
- cert-portal.siemens.com/productcert/html/ssa-082556.html
- cert-portal.siemens.com/productcert/html/ssa-032379.html
- cert-portal.siemens.com/productcert/html/ssa-457936.html
- lists.debian.org/debian-lts-announce/2025/10/msg00007.html
- cert-portal.siemens.com/productcert/html/ssa-019113.html
- lists.debian.org/debian-lts-announce/2025/10/msg00008.html
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 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-2025-38721 is "netfilter: ctnetlink: fix refcount leak on table dump", rated Medium. It affects Debian Linux (Debian); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. CVSS 5.5 describes technical severity. EPSS 0.17% 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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