CVE-2026-64253: kernel/fork: clear PF_BLOCK_TS in copy_process()

Severity: medium (CVSS 5.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.1% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-07-24 · updated 2026-08-17
Weakness: CWE-476

Description

In the Linux kernel, the following vulnerability has been resolved: kernel/fork: clear PF_BLOCK_TS in copy_process() PF_BLOCK_TS is only set in blk_time_get_ns() when current->plug is non-NULL, and blk_finish_plug() clears it via __blk_flush_plug() before NULLing the plug pointer. copy_process() breaks the invariant by inheriting PF_BLOCK_TS from the parent while resetting the child's plug to NULL. Clear PF_BLOCK_TS alongside that assignment so callers can rely on "PF_BLOCK_TS set implies current->plug != NULL" and dereference current->plug unguarded.

Affected products

Linux kernel: from 6.9 before 6.12.95; from 6.13 before 6.18.38; from 6.19 before 7.1.3 — fixed in 6.12.95, 6.18.38, 7.1.3

How to fix

Upgrade to a fixed version: Linux kernel 6.12.95, 6.18.38, 7.1.3. Check the vendor advisory for mitigations.

References

Get alerted when CVE-2026-64253 or the next vulnerability affects your stack