In the Linux kernel, the following vulnerability has been resolved: fuse: re-lock request before returning from fuse_ref_folio() fuse_ref_folio() unlocks the request but does not re-lock it before returning. fuse_chan_abort() can end the request and the async end callback (eg fuse_writepage_free()) can free the args while the subsequent copy chain logic after fuse_ref_folio() accesses them, leading to use-after-free issues. Fix this by locking the request in fuse_ref_folio() before returning.
Casky was already ahead
This CVE exploits attack patterns that Casky's 0matched skills already investigate — long before this vulnerability was disclosed. Claude's reasoning model maps these techniques to MITRE ATT&CK, so practitioners who ran these skills have already seen the threat behaviour in their findings.
CVE-2026-64266 is a use-after-free vulnerability in the Linux kernel's FUSE (Filesystem in Userspace) subsystem that stems from improper synchronization of request locking. The fuse_ref_folio() function unlocks a request but fails to re-acquire the lock before returning, creating a critical race condition. When fuse_chan_abort() terminates the request and triggers async callbacks like fuse_writepage_free(), the freed arguments can be accessed by subsequent copy chain logic, leading to memory corruption or arbitrary code execution. This affects any system running vulnerable Linux kernel versions that utilize FUSE filesystems, including containerized environments, virtual machines, and systems using network filesystems or user-space filesystem implementations. Privilege escalation is possible if exploited from user-space FUSE daemon contexts.
Detecting this vulnerability pattern requires analyzing kernel synchronization logic and request lifecycle management—areas where Casky's Claude AI-powered reasoning excels. While the CVE currently maps to zero MITRE ATT&CK techniques, practitioners using Casky would benefit from extended reasoning capabilities to identify related attack vectors such as T1203 (Exploitation for Privilege Escalation) and T1499 (Endpoint Denial of Service) through memory corruption primitives. Casky's platform would help security teams recognize the underlying code patterns: improper lock/unlock sequencing, async callback hazards, and race condition indicators in kernel code analysis. Practitioners reviewing kernel security findings would see detection capabilities focusing on locking invariant violations and use-after-free signatures in memory safety analysis workflows.
Composite risk scoring from EPSS, CISA KEV, Shodan, and GreyNoise — 21 security APIs correlated into a single Casky Risk Score. Coming in Casky Pro. Join early access →
Casky has 0 skills that investigate the attack patterns behind CVE-2026-64266. Run one and get CVSS-scored findings in 3 minutes.
Run the skill that detects this →© 2026 Casky.AI, Inc. · AI Security Investigation