CVE-2026-42391
published 2026-08-28CVE-2026-42391: An unauthenticated attacker can send an IMAP ID command with a very large number of parameters before logging in, which causes memory and CPU usage to grow…
PriorityP343high7.5CVSS 3.1
AVNACLPRNUINSUCNINAH
EPSS
0.45%
38.0th percentile
An unauthenticated attacker can send an IMAP ID command with a very large number of parameters before logging in, which causes memory and CPU usage to grow disproportionately. The login process can be terminated by the out-of-memory handling, which also terminates all other connections handled by the same process. This can cause degradation or denial of service for IMAP logins. Limit the number of connections handled by a single imap-login process. This has a performance impact though. Update to non-vulnerable version. No publicly available exploits are known.
Affected
5 ranges
| Vendor | Product | Version range | Fixed in |
|---|---|---|---|
| dovecot | dovecot | — | — |
| open-xchange_gmbh | ox_dovecot_ce | >= 2.3.0 < 2.4.5 | 2.4.5 |
| open-xchange_gmbh | ox_dovecot_pro | >= 2.3.0 < 2.3.22.2 | 2.3.22.2 |
| open-xchange_gmbh | ox_dovecot_pro | >= 3.0.0 < 3.0.7 | 3.0.7 |
| open-xchange_gmbh | ox_dovecot_pro | >= 3.1.0 < 3.1.6 | 3.1.6 |
CVSS provenance
nvdv3.17.5HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
vendor_redhat7.5HIGH
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GHSA
An unauthenticated attacker can send an IMAP ID command with a very large number of parameters before logging in, which causes memory and CPU usage to grow disproportionately.
ghsa_unreviewed·2026-08-28
CVE-2026-42391 [HIGH] CWE-400 An unauthenticated attacker can send an IMAP ID command with a very large number of parameters before logging in, which causes memory and CPU usage to grow disproportionately.
An unauthenticated attacker can send an IMAP ID command with a very large number of parameters before logging in, which causes memory and CPU usage to grow disproportionately. The login process can be terminated by the out-of-memory handling, which also terminates all other connections handled by the same process. This can cause degradation or denial of service for IMAP logins. Limit the number of connections handled by a single imap-login process. This has a performance impact though. Update to non-vulnerable version. No publicly available exploits are known.
Red Hat
dovecot: Dovecot: Denial of Service via IMAP ID command with excessive parameters
vendor_redhat·2026-08-28·CVSS 7.5
CVE-2026-42391 [HIGH] CWE-770 dovecot: Dovecot: Denial of Service via IMAP ID command with excessive parameters
dovecot: Dovecot: Denial of Service via IMAP ID command with excessive parameters
An unauthenticated attacker can send an IMAP ID command with a very large number of parameters before logging in, which causes memory and CPU usage to grow disproportionately. The login process can be terminated by the out-of-memory handling, which also terminates all other connections handled by the same process. This can cause degradation or denial of service for IMAP logins. Limit the number of connections handled by a single imap-login process. This has a performance impact though. Update to non-vulnerable version. No publicly available exploits are known.
A flaw was found in Dovecot. An unauthenticated attacker can send an IMAP ID command with a very large number of parameters before logging in. This a
No detection rules found.
No public exploits indexed.
Bugzilla
CVE-2026-42391 dovecot: Dovecot: Denial of Service via IMAP ID command with excessive parameters [fedora-all]
bugzilla·2026-09-01·CVSS 7.5
CVE-2026-42391 [HIGH] CVE-2026-42391 dovecot: Dovecot: Denial of Service via IMAP ID command with excessive parameters [fedora-all]
CVE-2026-42391 dovecot: Dovecot: Denial of Service via IMAP ID command with excessive parameters [fedora-all]
Disclaimer: Community trackers are created by Red Hat Product Security team on a best effort basis. Package maintainers are required to ascertain if the flaw indeed affects their package, before starting the update process.
An unauthenticated attacker can send an IMAP ID command with a very large number of parameters before logging in, which causes memory and CPU usage to grow disproportionately. The login process can be terminated by the out-of-memory handling, which also terminates all other connections handled by the same process. This can cause degradation or denial of service for IMAP logins. Limit the number of connections handled by a single imap-login process. This has a
Bugzilla
CVE-2026-42391 dovecot: Dovecot: Denial of Service via IMAP ID command with excessive parameters
bugzilla·2026-08-28·CVSS 7.5
CVE-2026-42391 [HIGH] CVE-2026-42391 dovecot: Dovecot: Denial of Service via IMAP ID command with excessive parameters
CVE-2026-42391 dovecot: Dovecot: Denial of Service via IMAP ID command with excessive parameters
An unauthenticated attacker can send an IMAP ID command with a very large number of parameters before logging in, which causes memory and CPU usage to grow disproportionately. The login process can be terminated by the out-of-memory handling, which also terminates all other connections handled by the same process. This can cause degradation or denial of service for IMAP logins. Limit the number of connections handled by a single imap-login process. This has a performance impact though. Update to non-vulnerable version. No publicly available exploits are known.
2026-08-28
Published