# CVE-2026-72068: posix-cpu-timers: Use u64 multiplication in update_rlimit_cpu()

Status: published. Published: 2026-08-15. Updated: 2026-11-06.

In the Linux kernel, the following vulnerability has been resolved:

posix-cpu-timers: Use u64 multiplication in update_rlimit_cpu()

update_rlimit_cpu() converts the RLIMIT_CPU value to nanoseconds with

        u64 nsecs = rlim_new * NSEC_PER_SEC;

On 32-bit kernels both rlim_new (unsigned long) and NSEC_PER_SEC
(1000000000L) are 32-bit, so the multiplication is performed in unsigned
long and truncated for rlim_new > 4 seconds before being widened to u64.

The same file already casts to u64 for the matching computation in
check_process_timers():

        u64 softns = (u64)soft * NSEC_PER_SEC;

As a result, the truncated value is installed into the CPUCLOCK_PROF
expiry cache (nextevt), causing the process CPU timer to be programmed
to fire prematurely for any RLIMIT_CPU soft limit >= 5 seconds. The
actual SIGXCPU/SIGKILL decision in check_process_timers() already casts
to u64 and is therefore correct, so limit enforcement is not broken;
only the expiry-cache programming is wrong. Apply the same cast here so
both paths convert rlim_cur identically.

64-bit kernels are unaffected.

## Remediation

No remediation reported in collected sources

## Affected products and versions

- Linux / Linux: ≥ 858cf3a8c59968e7c5f7c1a1192459a0d52d1ab4; < feb5c87c8514444ba891b75a5a3eae57c64edaf8 (affected, git); ≥ 858cf3a8c59968e7c5f7c1a1192459a0d52d1ab4; < 384628d6cdde0fcd76868606fad3ad8293100afb (affected, git); ≥ 858cf3a8c59968e7c5f7c1a1192459a0d52d1ab4; < 1fafc4d9b411645eb34de43362b966dc8fb3e263 (affected, git); ≥ 858cf3a8c59968e7c5f7c1a1192459a0d52d1ab4; < cff8281bacd2866767e6194c3079d33b6c5a74f4 (affected, git); ≥ 858cf3a8c59968e7c5f7c1a1192459a0d52d1ab4; < edf6babb9edd2d3e19229ade339081f439d4f478 (affected, git); ≥ 858cf3a8c59968e7c5f7c1a1192459a0d52d1ab4; < ea6a188ee805e841a0e242f14d15953e0dfa74bb (affected, git); ≥ 858cf3a8c59968e7c5f7c1a1192459a0d52d1ab4; < 571e1f10b5996ba3e4dc63ea77de4aa309c384ce (affected, git); ≥ 858cf3a8c59968e7c5f7c1a1192459a0d52d1ab4; < 26aff38fefb1d6cd87e22525f41cc8f1aa61b24f (affected, git). Source: CNA: Linux
- Linux / Linux: 4.11 (affected); ≥ 0; < 4.11 (unaffected, semver); ≥ 5.10.261; ≤ 5.10.* (unaffected, semver); ≥ 5.15.212; ≤ 5.15.* (unaffected, semver); ≥ 6.1.178; ≤ 6.1.* (unaffected, semver); ≥ 6.6.145; ≤ 6.6.* (unaffected, semver); ≥ 6.12.97; ≤ 6.12.* (unaffected, semver); ≥ 6.18.40; ≤ 6.18.* (unaffected, semver); ≥ 7.1.5; ≤ 7.1.* (unaffected, semver); ≥ 7.2; ≤ * (unaffected, original_commit_for_fix). Source: CNA: Linux

## Severity and prioritization

- CISA KEV: No listing in collected sources

- EPSS: 0.22% as of 2026-11-06; percentile 12.55%

- SSVC: exploitation none; automatable no; technical impact partial; source ADP: CISA-ADP

- Weaknesses: Not reported

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://git.kernel.org/stable/c/feb5c87c8514444ba891b75a5a3eae57c64edaf8 (CNA: Linux)

- https://git.kernel.org/stable/c/384628d6cdde0fcd76868606fad3ad8293100afb (CNA: Linux)

- https://git.kernel.org/stable/c/1fafc4d9b411645eb34de43362b966dc8fb3e263 (CNA: Linux)

- https://git.kernel.org/stable/c/cff8281bacd2866767e6194c3079d33b6c5a74f4 (CNA: Linux)

- https://git.kernel.org/stable/c/edf6babb9edd2d3e19229ade339081f439d4f478 (CNA: Linux)

- https://git.kernel.org/stable/c/ea6a188ee805e841a0e242f14d15953e0dfa74bb (CNA: Linux)

- https://git.kernel.org/stable/c/571e1f10b5996ba3e4dc63ea77de4aa309c384ce (CNA: Linux)

- https://git.kernel.org/stable/c/26aff38fefb1d6cd87e22525f41cc8f1aa61b24f (CNA: Linux)

- https://git.kernel.org/stable/c/1fafc4d9b411645eb34de43362b966dc8fb3e263 (416baaa9-dc9f-4396-8d5f-8c081fb06d67)

- https://git.kernel.org/stable/c/26aff38fefb1d6cd87e22525f41cc8f1aa61b24f (416baaa9-dc9f-4396-8d5f-8c081fb06d67)

- https://git.kernel.org/stable/c/384628d6cdde0fcd76868606fad3ad8293100afb (416baaa9-dc9f-4396-8d5f-8c081fb06d67)

- https://git.kernel.org/stable/c/571e1f10b5996ba3e4dc63ea77de4aa309c384ce (416baaa9-dc9f-4396-8d5f-8c081fb06d67)

- https://git.kernel.org/stable/c/cff8281bacd2866767e6194c3079d33b6c5a74f4 (416baaa9-dc9f-4396-8d5f-8c081fb06d67)

- https://git.kernel.org/stable/c/ea6a188ee805e841a0e242f14d15953e0dfa74bb (416baaa9-dc9f-4396-8d5f-8c081fb06d67)

- https://git.kernel.org/stable/c/edf6babb9edd2d3e19229ade339081f439d4f478 (416baaa9-dc9f-4396-8d5f-8c081fb06d67)

- https://git.kernel.org/stable/c/feb5c87c8514444ba891b75a5a3eae57c64edaf8 (416baaa9-dc9f-4396-8d5f-8c081fb06d67)

## Provenance

- CNA: Linux: https://www.cve.org/CVERecord?id=CVE-2026-72068; retrieved 2026-11-06; source updated 2026-11-06

- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-72068; retrieved 2026-11-06; source updated 2026-11-06

- FIRST EPSS: https://api.first.org/data/v1/epss?cve=CVE-2026-72068; retrieved 2026-11-06; source updated Not reported

Revision: 36c06d9371d37212e6b908c133c8af3275b9a9898a3128631f990d43585bb5b4

Canonical: https://y2.dev/cve/CVE-2026-72068

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