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6.5 Medium

CVE-2026-40017 An attacker that can send mail to a user can craft a message header whose values are chosen to collide in an internal…

Description

An attacker that can send mail to a user can craft a message header whose values are chosen to collide in an internal hash table, which makes the IMAP THREAD command consume CPU disproportionate to the size of the message. This is a separate issue from CVE-2026-40014 and is not addressed by that fix. Whenever a mail client issues a THREAD command on the affected mailbox, this can cause degradation or denial of service for IMAP. Monitor system for abnormal CPU usage, kill the offending process and remove the offending message from the affected mailbox. Update to non-vulnerable version. No publicly available exploits are known.

Affected products and versions

Product Affected versions Fixed in
OX Dovecot Pro 3.1 3.1.0 → < 3.1.6 3.1.6
OX Dovecot Pro 3.0 3.0.0 → < 3.0.7 3.0.7
OX Dovecot Pro 2.3 2.3.0 → < 2.3.22.2 2.3.22.2
OX Dovecot CE 2.3 2.3.0 → < 2.4.5 2.4.5

References

Timeline

  1. Published
  2. Last modified

Other CVEs of OX Dovecot Pro

The 44 CVEs of OX Dovecot Pro →
CVE-2026-73209 An attacker that has valid credentials can send crafted compressed data that causes the affected process to exhaust… 6.5 Medium CVE-2026-73208 An attacker that holds a token intended for a different purpose can authenticate, because when an OAuth2 token… 7.4 High CVE-2026-52687 An attacker that has valid credentials can select a compression algorithm for the IMAP connection whose decompression… 6.5 Medium CVE-2026-52681 Sieve CPU resource usage is tracked in the compiled script, so an attacker that has valid credentials can reset the… 3.1 Low
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