CVE-2026-27858
HighCVSS 7.5Exploitation Probability (EPSS)
Elevated risk57th percentile - higher than 57% of all known CVEs
Summary
A vulnerability in managesieve allows an attacker to send a specially crafted message before authentication, causing excessive memory allocation. This can crash the managesieve-login process and make the protocol unavailable.
Risk Assessment
The risk involves potential disruption of the managesieve service, which may impact email filtering availability in the organization. Repeated attacks can lead to prolonged unavailability.
Recommendation
It is recommended to restrict access to the managesieve protocol to trusted networks only, or install a fixed version of the software as soon as it becomes available.
Other vulnerabilities in managesieve
See all- CVE-2026-40016Medium
Attacker can upload a malicious Sieve script over ManageSieve service (or locally) to bypass configured CPU time limits for Sieve up to 130 times of the configured limit. Attacker can use this to degrade server performance and bypass configured CPU time limits for Sieve scripts. Install fixed version, or alternatively prevent direct access to Sieve scripts via ManageSieve or local access. No publicly available exploits are known.
- CVE-2025-59032High
A vulnerability in ManageSieve causes the service to crash when processing the AUTHENTICATE command with a literal as the SASL initial response. This can be exploited to repeatedly crash the service, making it unavailable for other users.
Original NVD description (English source)
Attacker can send a specifically crafted message before authentication that causes managesieve to allocate large amount of memory. Attacker can force managesieve-login to be unavailable by repeatedly crashing the process. Protect access to managesieve protocol, or install fixed version. No publicly available exploits are known.
Vulnerability data from NVD (NIST) · CISA KEV · EPSS