What is CVE-2025-52691?
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.
The record classifies CVE-2025-52691 under weakness class CWE-434. Its CVSS v3 base vector states that the flaw is reachable remotely over the network, needs no prior authentication, needs no user interaction, and has high impact on confidentiality, integrity, availability. 1 affected-product entry is recorded, across 1 vendor, listed below. The identifier was first published 306 days ago.
Severity and exploitation probability
- CVSS v3.1 base score
- 10 — CRITICAL
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H - EPSS (FIRST)
- 85.6% probability of exploitation in the next 30 days, higher than 99.7% of all scored CVEs
- CISA KEV
- Listed since 2026-01-26, federal remediation deadline 2026-02-16 — used in known ransomware campaigns
- Threadlinqs priority
- 10/10 — CISA lists it as used in ransomware, which Threadlinqs scores at the maximum
- Published
- 2025-12-29, last modified 2026-02-26
Is CVE-2025-52691 being exploited?
CISA added CVE-2025-52691 to the Known Exploited Vulnerabilities catalog on 2026-01-26, which means the agency holds evidence of exploitation in the wild; US federal civilian agencies had to remediate it by 2026-02-16 under BOD 22-01. CISA flags the vulnerability as one used in known ransomware campaigns. Weaponised exploit code for CVE-2025-52691 is publicly available. 9 public proof-of-concept repositories are tracked for this identifier. A ProjectDiscovery Nuclei detection template exists (http/cves/2025/CVE-2025-52691.yaml). It currently carries a trending score of 50 in the Threadlinqs vulnerability feed.
- rxerium/CVE-2025-52691 (github)
- watchtowrlabs/watchTowr-vs-SmarterMail-CVE-2025-52691 (github)
- DeathShotXD/CVE-2025-52691-APT-PoC (github)
- rimbadirgantara/CVE-2025-52691-poc (github)
- you-ssef9/CVE-2025-52691 (github)
- nxgn-kd01/smartermail-cve-scanner (github)
- Udyz/CVE-2025-52691 (github)
- mohammadzarnian1357/Ashwesker-CVE-2025-52691 (github)
Affected products and versions
- Smartertools: Smartermail
How to fix CVE-2025-52691
The record marks a vendor fix as available for CVE-2025-52691. Patch reference: https://www.zimbra.com/security-advisories/cve-2025-52691/. Because CVE-2025-52691 is KEV-listed, US federal civilian agencies were required to apply the vendor fix, or stop using the product, by 2026-02-16. Apply the vendor fix referenced above to every affected product listed in this record, then confirm the running version against the vendor advisory.
Threat activity tracking CVE-2025-52691
2 tracked threats in the Threadlinqs corpus reference CVE-2025-52691, either in the campaign’s CVE list or as an indicator on the campaign record.
- Storm-1175 Medusa Ransomware Zero-Day Exploitation Campaign (CVE-2026-23760, CVE-2025-10035) — CRITICAL · 2026-04-06
- SmarterMail Dual-CVE Pre-Auth RCE Chain — CVE-2026-23760 Admin Password Reset + CVE-2026-24423 ConnectToHub RCE, CISA KEV, Mass Automated Exploitation, 2-Day Patch Weaponization via .NET Decompiler — CRITICAL · 2026-02-05
Sources
Enriched from CVE.org, FIRST EPSS, CISA KEV, public proof-of-concept repositories, ProjectDiscovery Nuclei. Last verified by Threadlinqs on .