---
id: CVE-2026-72068
title: 'posix-cpu-timers: Use u64 multiplication in update_rlimit_cpu()'
summary: |-
  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 * N…
severity: none
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= 858cf3a8c59968e7c5f7c1a1192459a0d52d1ab4 <
    feb5c87c8514444ba891b75a5a3eae57c64edaf8
  - >-
    Linux >= 858cf3a8c59968e7c5f7c1a1192459a0d52d1ab4 <
    384628d6cdde0fcd76868606fad3ad8293100afb
  - >-
    Linux >= 858cf3a8c59968e7c5f7c1a1192459a0d52d1ab4 <
    1fafc4d9b411645eb34de43362b966dc8fb3e263
  - >-
    Linux >= 858cf3a8c59968e7c5f7c1a1192459a0d52d1ab4 <
    cff8281bacd2866767e6194c3079d33b6c5a74f4
  - >-
    Linux >= 858cf3a8c59968e7c5f7c1a1192459a0d52d1ab4 <
    edf6babb9edd2d3e19229ade339081f439d4f478
  - >-
    Linux >= 858cf3a8c59968e7c5f7c1a1192459a0d52d1ab4 <
    ea6a188ee805e841a0e242f14d15953e0dfa74bb
  - >-
    Linux >= 858cf3a8c59968e7c5f7c1a1192459a0d52d1ab4 <
    571e1f10b5996ba3e4dc63ea77de4aa309c384ce
  - >-
    Linux >= 858cf3a8c59968e7c5f7c1a1192459a0d52d1ab4 <
    26aff38fefb1d6cd87e22525f41cc8f1aa61b24f
  - Linux 4.11
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: partial
  timestamp: '2026-11-06T16:51:04.940462Z'
published: '2026-08-15'
updated: '2026-11-06'
sourceUpdated: '2026-11-06T16:55:19.267Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-72068'
references:
  - url: 'https://git.kernel.org/stable/c/feb5c87c8514444ba891b75a5a3eae57c64edaf8'
  - url: 'https://git.kernel.org/stable/c/384628d6cdde0fcd76868606fad3ad8293100afb'
  - url: 'https://git.kernel.org/stable/c/1fafc4d9b411645eb34de43362b966dc8fb3e263'
  - url: 'https://git.kernel.org/stable/c/cff8281bacd2866767e6194c3079d33b6c5a74f4'
  - url: 'https://git.kernel.org/stable/c/edf6babb9edd2d3e19229ade339081f439d4f478'
  - url: 'https://git.kernel.org/stable/c/ea6a188ee805e841a0e242f14d15953e0dfa74bb'
  - url: 'https://git.kernel.org/stable/c/571e1f10b5996ba3e4dc63ea77de4aa309c384ce'
  - url: 'https://git.kernel.org/stable/c/26aff38fefb1d6cd87e22525f41cc8f1aa61b24f'
tags:
  - cve.org
epss: 0.0022
epssPercentile: 0.12538
ingestedAt: '2026-11-06T18:00:12.599Z'
---

## Overview

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.

## Affected

- `Linux >= 858cf3a8c59968e7c5f7c1a1192459a0d52d1ab4 < feb5c87c8514444ba891b75a5a3eae57c64edaf8`
- `Linux >= 858cf3a8c59968e7c5f7c1a1192459a0d52d1ab4 < 384628d6cdde0fcd76868606fad3ad8293100afb`
- `Linux >= 858cf3a8c59968e7c5f7c1a1192459a0d52d1ab4 < 1fafc4d9b411645eb34de43362b966dc8fb3e263`
- `Linux >= 858cf3a8c59968e7c5f7c1a1192459a0d52d1ab4 < cff8281bacd2866767e6194c3079d33b6c5a74f4`
- `Linux >= 858cf3a8c59968e7c5f7c1a1192459a0d52d1ab4 < edf6babb9edd2d3e19229ade339081f439d4f478`
- `Linux >= 858cf3a8c59968e7c5f7c1a1192459a0d52d1ab4 < ea6a188ee805e841a0e242f14d15953e0dfa74bb`
- `Linux >= 858cf3a8c59968e7c5f7c1a1192459a0d52d1ab4 < 571e1f10b5996ba3e4dc63ea77de4aa309c384ce`
- `Linux >= 858cf3a8c59968e7c5f7c1a1192459a0d52d1ab4 < 26aff38fefb1d6cd87e22525f41cc8f1aa61b24f`
- `Linux 4.11`

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.