Vulnerability Description
Sending "NOOP (((...)))" command with 4000 parenthesis open+close results in ~1MB extra memory usage. Longer commands will result in client disconnection. This 1 MB can be left allocated for longer time periods by not sending the command ending LF. So attacker could connect possibly from even a single IP and create 1000 connections to allocate 1 GB of memory, which would likely result in reaching VSZ limit and killing the process and its other proxied connections. Attacker could connect possibly from even a single IP and create 1000 connections to allocate 1 GB of memory, which would likely result in reaching VSZ limit and killing the process and its other proxied connections. Install fixed version, there is no other remediation. No publicly available exploits are known.
CVSS Score
MEDIUM
Affected Products
| Vendor | Product | Versions |
|---|---|---|
| Dovecot | Dovecot | < 2.4.3 |
| Open-Xchange | Dovecot | < 2.3.22.1 |
Related Weaknesses (CWE)
References
FAQ
What is CVE-2026-27857?
CVE-2026-27857 is a vulnerability with a CVSS score of 4.3 (MEDIUM). Sending "NOOP (((...)))" command with 4000 parenthesis open+close results in ~1MB extra memory usage. Longer commands will result in client disconnection. This 1 MB can be left allocated for longer ti...
How severe is CVE-2026-27857?
CVE-2026-27857 has been rated MEDIUM with a CVSS base score of 4.3/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2026-27857?
Check the references section above for vendor advisories and patch information. Affected products include: Dovecot Dovecot, Open-Xchange Dovecot.