SB20260720288 - Use-after-free in Linux kernel block zram driver
Published: July 20, 2026
Security Bulletin ID
SB20260720288
CSH Severity
Low
Patch available
YES
Number of vulnerabilities
1
Exploitation vector
Local access
Highest impact
Denial of service
Breakdown by Severity
- Low
- Medium
- High
- Critical
Description
This security bulletin contains information about 1 vulnerability.
1) Use-after-free (CVE-ID: CVE-2026-63951)
CWE-ID: CWE-416 - Use After Free
CVSSv4: 6.8 [CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N]
The vulnerability allows a local user to cause a denial of service.
The vulnerability exists due to a use-after-free in zram_writeback_endio when handling bio completion during writeback operations. A local user can trigger a race condition to cause a denial of service.
The issue occurs because the writeback control structure can be freed by the writeback task before wake_up() is invoked in the bio completion handler.
Remediation
Install update from vendor's website.