VulnerabilityPublished 18 Oct 2026

CVE-2026-98818: Linux kernel · mm/slab: do not wake up kswapd in __kfree_rcu_sheaf()

Affects Linux kernelSource CVE Database V5

Not known to be exploited : upgrade to af2fb3ee6679b517e2fdbd3ba16ec276a8b74312 or 46545c86b54ffb969b6e3662942b4a6191619eaa soon.

Data as of 26 Oct 2026, 14:05 UTC

Severity

High

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

EPSS: 0.1% chance of exploitation in 30 days – higher than 5% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in af2fb3ee6679b517e2fdbd3ba16ec276a8b74312, 46545c86b54ffb969b6e3662942b4a6191619eaa

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.

What to do

Upgrade Linux kernel to af2fb3ee6679b517e2fdbd3ba16ec276a8b74312 or 46545c86b54ffb969b6e3662942b4a6191619eaa.

Affected software

Product	Affected	Fixed in
LinuxLinux	Affected ≥ ec66e0d599520ab414db745544e25d80d0ac5054, < af2fb3ee6679b517e2fdbd3ba16ec276a8b74312	Fixed in af2fb3ee6679b517e2fdbd3ba16ec276a8b74312
LinuxLinux	Affected ≥ ec66e0d599520ab414db745544e25d80d0ac5054, < 46545c86b54ffb969b6e3662942b4a6191619eaa	Fixed in 46545c86b54ffb969b6e3662942b4a6191619eaa
LinuxLinux	Affected =6.18	Fixed in–

AI-suggested

A fix is available and has been applied in Linux kernel version 6.18 via specific commits. Users and administrators should update to the fixed kernel version to mitigate this deadlock vulnerability. No additional mitigation steps are required beyond applying the official fix.

Description

A deadlock vulnerability in the Linux kernel's memory management subsystem was fixed by preventing the wake-up of kswapd within the __kfree_rcu_sheaf() function. The issue arises because kfree_rcu() can be called while holding pi_lock, and waking kswapd under this lock leads to a circular locking dependency and potential deadlock. The deadlock was verified using a modified kernel with lock dependency detection. This flaw affects Linux kernel version 6.18 and was resolved in specific commits.

Impact

The vulnerability can cause a kernel deadlock due to a circular locking dependency involving pi_lock and kswapd wake-up. This deadlock can halt kernel operations that rely on memory freeing under certain locking conditions, potentially leading to system hangs or crashes. However, reproducing the issue intentionally is difficult, and no known exploits in the wild have been reported.

Summary

CVE-2026-98818 addresses a deadlock condition in the Linux kernel's slab allocator where __kfree_rcu_sheaf() wakes up the kswapd kernel thread while holding pi_lock, a raw spinlock in the scheduler. Since kfree_rcu() may be called under pi_lock, waking kswapd—which also tries to acquire pi_lock—creates a circular locking dependency causing a deadlock. The vulnerability was confirmed through lockdep warnings in a modified kernel. The fix involves ensuring that kfree_rcu() does not allocate memory with __GFP_KSWAPD_RECLAIM, thereby avoiding waking kswapd under pi_lock. This issue was resolved in Linux kernel version 6.18 via commits af2fb3ee6679b517e2fdbd3ba16ec276a8b74312 and 46545c86b54ffb969b6e3662942b4a6191619eaa.

References

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 26 Oct 2026, 09:43 UTC

Technical details

References

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