Description

An attacker that has valid credentials can open many connections to the imap-hibernate service and send invalid commands, which can intermittently cause an out-of-bounds read and crash the process. The crash interrupts hibernated IMAP sessions handled by the affected process, which can cause degradation of service for IMAP. Disable IMAP hibernation. Update to non-vulnerable version. No publicly available exploits are known.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "4.3",
  "pubDate": "2026-08-28T12:16:28.363Z",
  "pubdate": "2026-08-28T12:16:28.363Z",
  "executiveSummary": "A critical memory safety vulnerability exists in the imap-hibernate service, characterized as an out-of-bounds (OOB) read condition.\nThe vulnerability allows an authenticated attacker to trigger an application crash, resulting in a denial-of-service (DoS) condition by interrupting active hibernated IMAP sessions.\nExploitation requires valid user credentials, meaning the attacker must be authorized within the system environment to initiate the attack vector.\nThe impact is primarily availability-based, leading to service degradation or total interruption for legitimate users relying on hibernated IMAP processes.\nWhile no public exploits are currently identified, the nature of the flaw poses a significant operational risk to system stability.\nMitigation requires disabling the affected IMAP hibernation functionality and applying vendor-supplied updates to reach a non-vulnerable version.",
  "technicalDetails": "The vulnerability originates from improper memory handling within the imap-hibernate service when processing incoming IMAP command strings. Specifically, the service fails to sufficiently validate the bounds of data input provided by a connected client before attempting to access memory addresses associated with active session states.\nThe attack flow begins with an authenticated attacker establishing multiple concurrent network connections to the imap-hibernate service. Upon establishing these sessions, the attacker deliberately injects malformed or invalid IMAP commands crafted to trigger an erroneous read operation beyond the intended memory buffers.\nWhen the service logic processes these malicious packets, the out-of-bounds read occurs. Because the memory access falls outside the valid memory range allocated for the specific IMAP session context, the underlying operating system or language runtime detects an invalid memory access or segmentation fault, resulting in an immediate process crash.\nThe primary component affected is the session management logic within imap-hibernate that handles hibernated states. When the process terminates unexpectedly, all IMAP sessions currently held in a hibernated state by that process are lost or interrupted, causing an immediate disruption of service for all users whose sessions were managed by the crashed instance.\nExploitation is strictly contingent upon the attacker possessing valid authentication credentials for the target environment. The network exposure is limited to systems where imap-hibernate is enabled and accessible via the IMAP protocol. The payload itself does not require complex memory corruption primitives such as heap spraying or ROP chains; rather, it relies on the application's failure to handle non-conforming command inputs gracefully during the state-restoration or idle-handling phases of the IMAP protocol.\nPost-exploitation, the service remains unavailable to the affected users until the service is manually restarted or recovered by the supervisor process. Repeated successful exploitation can result in a persistent denial-of-service state, rendering the imap-hibernate feature functionally useless."
}