VulnerabilityPublished 19 Jul 2026Updated 6 Nov 2026

CVE-2026-63804: Linux kernel · gfs2: fix use-after-free in gfs2_qd_dealloc

Affects Linux kernelSource CVE Database V5

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Not known to be exploited · fixed in f9c9ec2c319f843b70ecdf939d48b52d189bc081 : update Linux kernel when convenient.

Data as of 6 Nov 2026, 16:49 UTC

Severity

Unrated

Rated by Threat Radar · No CVSS score from NVD or the CNA

Thin evidence

One scorer or none

Exploitation: No evidence of active exploitation and no public proof of concept
Automatable: Attackers cannot reliably automate steps 1–4 of the kill chain
Technical impact: Limited control over the software or limited information exposure

CISA SSVC assessment, 2026-11-06.

Patch

Available – fixed in f9c9ec2c319f843b70ecdf939d48b52d189bc081, b85ef03f726b15047a6fa6d11b639bdf6c0ee4f0, 8745d9f7e1682c39f0a1578895ac74205e2a6757 +2

Exploitation evidence

Disclosed: evidence found.
CVE published 19 Jul 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: 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 6 Nov 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.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), 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 ≥ a475c5dd16e57c570113eccba51955b5df8bb052, < f9c9ec2c319f843b70ecdf939d48b52d189bc081	Fixed in f9c9ec2c319f843b70ecdf939d48b52d189bc081
LinuxLinux	Affected ≥ a475c5dd16e57c570113eccba51955b5df8bb052, < b85ef03f726b15047a6fa6d11b639bdf6c0ee4f0	Fixed in b85ef03f726b15047a6fa6d11b639bdf6c0ee4f0
LinuxLinux	Affected ≥ a475c5dd16e57c570113eccba51955b5df8bb052, < 8745d9f7e1682c39f0a1578895ac74205e2a6757	Fixed in 8745d9f7e1682c39f0a1578895ac74205e2a6757
LinuxLinux	Affected ≥ a475c5dd16e57c570113eccba51955b5df8bb052, < 9d0d5ba20cad661f7f287d4c66d2c19022ce2fd0	Fixed in 9d0d5ba20cad661f7f287d4c66d2c19022ce2fd0
LinuxLinux	Affected ≥ a475c5dd16e57c570113eccba51955b5df8bb052, < 4fe388218826df8607ae41a6305df67db08a9093	Fixed in 4fe388218826df8607ae41a6305df67db08a9093
LinuxLinux	Affected =6.6	Fixed in–

Description

In the Linux kernel, the following vulnerability has been resolved: gfs2: fix use-after-free in gfs2_qd_dealloc gfs2_qd_dealloc(), called as an RCU callback from gfs2_qd_dispose(), accesses the superblock object sdp through qd->qd_sbd after freeing qd. It does so to decrement sd_quota_count and wake up sd_kill_wait. However, by the time the RCU callback runs, gfs2_put_super() may have already freed sdp via free_sbd(). This can happen when gfs2_quota_cleanup() is called during unmount: it disposes of quota objects via call_rcu() and then waits on sd_kill_wait with a 60-second timeout. If the timeout expires, or if gfs2_gl_hash_clear() triggers additional qd_put() calls that schedule more RCU callbacks after the wait completes, gfs2_put_super() will proceed to free the superblock while RCU callbacks referencing it are still pending. Add an rcu_barrier() before free_sbd() in gfs2_put_super() to ensure all pending RCU callbacks (including gfs2_qd_dealloc) have completed before the superblock is freed.

References

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