CVE-2025-52691 — Smartermail
CRITICALCVE-2025-52691 is a critical-severity (CVSS 10) Unrestricted File Upload vulnerability in smartertools smartermail. It is in CISA's Known Exploited Vulnerabilities catalog (added 2026-01-26) and has been used in ransomware campaigns — treat it as actively exploited and patch now. A fix is available — see the affected versions and patch details below.
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.
Exploitation Status
Actively exploited in the wild
- Confirmed by CISA's Known Exploited Vulnerabilities catalog on 2026-01-26 — including use in ransomware campaigns. Federal agencies were required to remediate by 2026-02-16.
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
- A successful exploit gives an attacker total control of the affected component, not partial access.
Exploitation and automatability from CISA (KEV catalog and SSVC triage) for CVE-2025-52691.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
CVE-2025-52691 by exploitation likelihood (EPSS) against impact (CVSS). In the shaded patch-first corner (EPSS 50%+, CVSS 7.0+).
Where this sits among everything scored
Of 395,249 CVEs with a current EPSS score, this one falls in the 50–90% band (highlighted). Counts from FIRST.org, log-scaled.
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.
Affected Products
smartermailsmartertoolsResearch use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.
rxerium/CVE-2025-52691
Detection for CVE-2025-52691
watchtowrlabs/watchTowr-vs-SmarterMail-CVE-2025-52691
DeathShotXD/CVE-2025-52691-APT-PoC
An enhanced proof-of-concept exploit for CVE-2025-52691 (SmarterMail Arb
rimbadirgantara/CVE-2025-52691-poc
Detection & mitigation playbook
Vendor / applianceDetect
Inventory every smartertools smartermail deployment and check each version against the affected-products list above.
Fix
Apply the smartertools smartermail security patch or hotfix for CVE-2025-52691 on the affected version, following the vendor advisory for your exact build.
Workarounds
Treat uploaded files as untrusted until proven otherwise: validate the actual content type rather than the supplied extension, store uploads outside the web root on a volume mounted without execute permission, and rename them to server-generated identifiers so an attacker cannot choose the path a request will later resolve. Alongside that, restrict the management interface to trusted networks and apply the vendor's recommended configuration mitigations.
How to detect CVE-2025-52691
A community-maintained Nuclei template exists for this CVE. You can scan for it directly:
nuclei -id cve-2025-52691 -u https://target- Template
- SmarterMail - Unrestricted File Upload
- Severity
- critical
- Impact
- Unauthenticated attackers can upload arbitrary files, potentially leading to remote code execution and full server compromise.
- Remediation
- Update to the latest version of the mail server.
Template by ProjectDiscovery nuclei-templates (DhiyaneshDK, watchTowr), MIT licensed. View the full template. Scan only systems you are authorised to test.
Frequently Asked Questions
Is CVE-2025-52691 being exploited in your environment?
Detect and block the exploit chain at execution, on systems you cannot patch yet.