CVE-2026-31586
Description
A flaw was found in the Linux kernel's block control group (blk-cgroup) component. A timing issue in the cgwb_release_workfn() function can lead to a use-after-free vulnerability. This occurs when a block control group object is prematurely released while still being referenced. A local attacker could exploit this to cause system instability or a denial of service.
Statement
A use-after-free flaw in the Linux kernel cgroup writeback and block cgroup interaction can occur when cgwb_release_workfn() drops the last reference to wb->blkcg_css before later passing the same pointer to blkcg_unpin_online(). A local attacker with access to cgroup/writeback lifecycle operations could potentially race cgroup destruction and trigger a kernel crash. The most likely impact is denial of service, while privilege escalation would require additional, unproven heap reuse control. The bug appears more consistent with a denial-of-service race condition than a reliably exploitable privilege-escalation issue, as it involves a narrow worker-thread race with no obvious attacker-controlled overwrite or reclaim primitive and currently reproduces mainly as a KASAN-detected crash.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
The following CVSS metrics and score provided are preliminary and subject to review.
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 7 | N/A | 7.8 |
| Attack Vector | Local | N/A | Local |
| Attack Complexity | High | N/A | Low |
| Privileges Required | Low | N/A | Low |
| User Interaction | None | N/A | None |
| Scope | Unchanged | N/A | Unchanged |
| Confidentiality | High | N/A | High |
| Integrity Impact | High | N/A | High |
| Availability Impact | High | N/A | High |
Vector
Red Hat: CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
cve.org: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Understanding the Weakness (CWE)
Integrity,Other
Technical Impact: Alter Execution Logic; Unexpected State
The main problem is that -- if a lock is overcome -- data could be altered in a bad state.
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