VulnerabilityPublished 18 Oct 2026

CVE-2026-98484: Linux kernel · netfilter: nf_tables: skip expired catchall elements on insert and delete

Source GCVE Database

Authoritative record:CVE-2026-98484

Not known to be exploited · fixed in 70194dc37670bd08e44b471389861cc01bd3a3c9 : update Linux kernel when convenient.

Data as of 26 Oct 2026, 13:47 UTC

Severity

Medium

Rated by Threat Radar · CVSS not yet scored by NVD

EPSS: 0.2% chance of exploitation in 30 days – higher than 9% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 70194dc37670bd08e44b471389861cc01bd3a3c9, 12cf803edfffef96f6415f0b5dbc7ec88842ea0f, 5e20b39aa7844769a7a782484bc1a809ffbc513e +2

Exploitation evidence

Disclosed: evidence found.
CVE published 18 Oct 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

ghsa-j4h7-w628-h5g3

What to do

Upgrade to a fixed release listed under Affected software.

Affected software

Product	Affected	Fixed in
LinuxLinux	Affected ≥ aaa31047a6d25da0fa101da1ed544e1247949b40, < 70194dc37670bd08e44b471389861cc01bd3a3c9	Fixed in 70194dc37670bd08e44b471389861cc01bd3a3c9
LinuxLinux	Affected ≥ aaa31047a6d25da0fa101da1ed544e1247949b40, < 12cf803edfffef96f6415f0b5dbc7ec88842ea0f	Fixed in 12cf803edfffef96f6415f0b5dbc7ec88842ea0f
LinuxLinux	Affected ≥ aaa31047a6d25da0fa101da1ed544e1247949b40, < 5e20b39aa7844769a7a782484bc1a809ffbc513e	Fixed in 5e20b39aa7844769a7a782484bc1a809ffbc513e
LinuxLinux	Affected ≥ aaa31047a6d25da0fa101da1ed544e1247949b40, < 4fb8b1ccc475651e480e509de126bb9ce7f3cff9	Fixed in 4fb8b1ccc475651e480e509de126bb9ce7f3cff9
LinuxLinux	Affected ≥ aaa31047a6d25da0fa101da1ed544e1247949b40, < 2f07da3881525f7cbfed1ced2796c71a201505b9	Fixed in 2f07da3881525f7cbfed1ced2796c71a201505b9
LinuxLinux	Affected =5.13	Fixed in–

AI-suggested

A fix has been implemented in the Linux kernel to address this issue by aligning the insert, delete, lookup, and dump operations to consistently skip expired catchall elements and properly manage garbage collection. Users should apply the official kernel updates that include this fix. Patch status is not explicitly stated in the provided data; therefore, check the vendor or Linux kernel advisory for the current remediation guidance.

Description

A vulnerability in the Linux kernel's netfilter nf_tables subsystem involves improper handling of expired catchall elements during insert and delete operations. Expired catchall elements become invisible to userspace dumps but still block re-insertion attempts, causing silent failures or errors. This can lead to stale entries persisting until garbage collection occurs, potentially causing catchall rules to stop matching unexpectedly. The issue affects the logic for detecting duplicates and deleting elements, resulting in inconsistent behavior between userspace visibility and kernel state.

Impact

The vulnerability causes stale catchall elements with expired timeouts to persist invisibly in the kernel, blocking re-insertion of new elements and causing silent failures or errors in rule management. This may lead to catchall rules silently ceasing to match traffic for an arbitrarily long time until garbage collection removes the stale entries. The inconsistency between userspace visibility and kernel state can disrupt expected firewall or packet filtering behavior.

Summary

The vulnerability in the Linux kernel's netfilter nf_tables subsystem arises because nft_setelem_catchall_insert() only checks duplicates against active elements, while other lookup and dump functions skip expired elements. When a catchall element expires, it becomes invisible to userspace but still blocks re-insertion, causing requests with NLM_F_EXCL to fail with -EEXIST and others to silently do nothing. Similarly, the delete function may deactivate stale expired entries instead of fresh ones, leading to inconsistencies. The fix aligns all walks to consider only active and non-expired elements using a per-network namespace timestamp at transaction start, ensuring consistent behavior and proper garbage collection synchronization.

References

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