CVE-2026-89765 timers/itimer: Zero-init old itimerval before copy to userspace
Local attackers can read uninitialized kernel memory via getitimer on sparc64 due to missing zero-initialization of padding bytes.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-89765?
CVE-2026-89765 is a vulnerability in Linux, published on 11 Sep 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
timers/itimer: Zero-init old itimerval before copy to userspace
On native sparc64, struct __kernel_old_timeval contains a four-byte hole after tv_usec because tv_sec is 64-bit while __kernel_suseconds_t is 32-bit. put_itimerval() fills only the named fields in a stack-allocated __kernel_old_itimerval and copies the entire object to userspace, so getitimer() can expose the two padding holes.
Zero-initialize the aggregate before assigning the fields so implicit padding is deterministic before it crosses the user/kernel boundary.
Which versions are affected by CVE-2026-89765?
How do I fix CVE-2026-89765?
Apply the vendor's patch.
Is CVE-2026-89765 being exploited?
There is no known exploitation of CVE-2026-89765 in the wild and no public exploit code.
Sources
Also known as AZL-100623, BELL-CVE-2026-89765, DEBIAN-CVE-2026-89765, GHSA-x38g-mr96-v378, UBUNTU-CVE-2026-89765.