VulnerabilityPublished 23 Oct 2026Updated 26 Oct 2026

CVE-2026-98881: Linux kernel · net: bridge: remove stale rcu_barrier() in br_multicast_dev_del()

Affects Linux kernelSource CVE Database V5

Not known to be exploited · fixed in f0018acf0b66f93a292667c9a9c2a26c570cf270 : update Linux kernel when convenient.

Data as of 26 Oct 2026, 13:07 UTC

Severity

Medium

Rated Medium by Threat Radar's AI analysis · CVSS not yet scored by NVD

EPSS: 0.1% chance of exploitation in 30 days – higher than 7% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in f0018acf0b66f93a292667c9a9c2a26c570cf270, ac0e823a228f94ad9d7a3d876cc07e59a7afb806, 39679927fa7aaf4601119f7234342d1b5d4f6f84 +4

Exploitation evidence

Disclosed: evidence found.
CVE published 23 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.

What to do

Upgrade to a fixed release listed under Affected software.

Affected software

Product	Affected	Fixed in
LinuxLinux	Affected ≥ 19e3a9c90c53479fecaa02307bf2db5ab8b3ffe3, < f0018acf0b66f93a292667c9a9c2a26c570cf270	Fixed in f0018acf0b66f93a292667c9a9c2a26c570cf270
LinuxLinux	Affected ≥ 19e3a9c90c53479fecaa02307bf2db5ab8b3ffe3, < ac0e823a228f94ad9d7a3d876cc07e59a7afb806	Fixed in ac0e823a228f94ad9d7a3d876cc07e59a7afb806
LinuxLinux	Affected ≥ 19e3a9c90c53479fecaa02307bf2db5ab8b3ffe3, < 39679927fa7aaf4601119f7234342d1b5d4f6f84	Fixed in 39679927fa7aaf4601119f7234342d1b5d4f6f84
LinuxLinux	Affected ≥ 19e3a9c90c53479fecaa02307bf2db5ab8b3ffe3, < 0443f6aac6bf6a91e406273fdda11497cef6ad07	Fixed in 0443f6aac6bf6a91e406273fdda11497cef6ad07
LinuxLinux	Affected ≥ 19e3a9c90c53479fecaa02307bf2db5ab8b3ffe3, < 372ee8fbe0f796031c60f676ec90f0788c26523d	Fixed in 372ee8fbe0f796031c60f676ec90f0788c26523d
LinuxLinux	Affected ≥ 19e3a9c90c53479fecaa02307bf2db5ab8b3ffe3, < 35f9f11740515a10b084adfb1ce691351f2452ab	Fixed in 35f9f11740515a10b084adfb1ce691351f2452ab

AI-suggested

A fix is available and has been applied in the Linux kernel source. Users should update to the fixed kernel versions or apply the relevant patches to remove the stale rcu_barrier() call in br_multicast_dev_del(). No additional mitigation is required beyond applying the official fix.

Description

A vulnerability in the Linux kernel's network bridge code involved a stale rcu_barrier() call in the br_multicast_dev_del() function. This call was a remnant from earlier code using call_rcu() and caused excessive RTNL (routing netlink) pressure, leading to blocked tasks and potential performance degradation. The issue has been resolved by removing the obsolete rcu_barrier() call, which is no longer necessary due to the use of kfree_rcu().

Impact

The vulnerability caused extreme RTNL pressure in the kernel, leading to blocked tasks and potential system performance degradation or hangs during network namespace cleanup. It primarily affects the Linux kernel's network bridge functionality, potentially impacting systems using bridging features. There is no indication of direct security compromise or exploitation in the wild.

Summary

The Linux kernel contained a stale rcu_barrier() call in the br_multicast_dev_del() function within net/bridge/br_multicast.c. This call originated from when call_rcu() was used but became problematic after switching to kfree_rcu(), causing extreme RTNL pressure and task blocking as reported by syzbot. The fix involved removing this obsolete rcu_barrier() to alleviate the RTNL contention and improve kernel stability during network namespace cleanup.

References

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 26 Oct 2026, 09:31 UTC

Technical details

References

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