CVE-2026-27852

NameCVE-2026-27852
DescriptionAn attacker that can send mail to a user can craft a message whose headers contain a very large number of email addresses or MIME parameters, which causes excessive memory usage when the message is later parsed. The message is still delivered, but reading it over IMAP can exhaust the memory limit of the process and terminate it, causing denial of service for the affected user. Update to non-vulnerable version. No publicly available exploits are known.
SourceCVE (at NVD; CERT, ENISA, LWN, oss-sec, fulldisc, Debian ELTS, Red Hat, Ubuntu, Gentoo, SUSE bugzilla/CVE, GitHub advisories/code/issues, web search, more)
Debian Bugs1146018

Vulnerable and fixed packages

The table below lists information on source packages.

Source PackageReleaseVersionStatus
dovecot (PTS)bookworm, bookworm (security)1:2.3.19.1+dfsg1-2.1+deb12u6vulnerable
trixie (security), trixie1:2.4.1+dfsg1-6+deb13u6vulnerable
forky, sid1:2.4.5+dfsg1-2fixed

The information below is based on the following data on fixed versions.

PackageTypeReleaseFixed VersionUrgencyOriginDebian Bugs
dovecotsource(unstable)1:2.4.5+dfsg1-11146018

Notes

https://documentation.open-xchange.com/dovecot/security/advisories/html/2026/oxdc-adv-2026-0003.html#cve-2026-27852-dos-by-sending-mail-with-bad-header

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