Description
Very large headers can cause resource exhaustion when parsing message. The message-parser normally reads reasonably sized chunks of the message. However, when it feeds them to message-header-parser, it starts building up "full_value" buffer out of the smaller chunks. The full_value buffer has no size limit, so large headers can cause large memory usage. It doesn't matter whether it's a single long header line, or a single header split into multiple lines. This bug exists in all Dovecot versions. Incoming mails typically have some size limits set by MTA, so even largest possible header size may still fit into Dovecot's vsz_limit. So attackers probably can't DoS a victim user this way. A user could APPEND larger mails though, allowing them to DoS themselves (although maybe cause some memory issues for the backend in general). One can implement restrictions on headers on MTA component preceding Dovecot. No publicly available exploits are known.
Affected products
| Vendor | Product | Affected | Fixed |
|---|---|---|---|
| Open-Xchange | OX Dovecot Pro | ≤ 2.3.21 | — |
Fixed in Linux distributions
Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.
Debian
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian 14 | dovecot | 1:2.3.21.1+dfsg1-1 | — |
| Debian 13 | dovecot | 1:2.3.21.1+dfsg1-1 | — |
| Debian 12 | dovecot | 1:2.3.19.1+dfsg1-2.1+deb12u1 | DSA-5752-1 |
| Debian 11 | dovecot | 1:2.3.13+dfsg1-2+deb11u2 | DLA-3860-1 |
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 24.04 LTS | dovecot | 1:2.3.21+dfsg1-2ubuntu6 | USN-6982-1 |
| Ubuntu 22.04 LTS | dovecot | 1:2.3.16+dfsg1-3ubuntu2.4 | USN-7013-1 |
| Ubuntu 20.04 LTS | dovecot | 1:2.3.7.2-1ubuntu3.7 | USN-7013-1 |
| Ubuntu 18.04 LTS | dovecot | No fix yet | — |
| Ubuntu 16.04 LTS | dovecot | No fix yet | — |
Show 1 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu Pro 14.04 LTS | dovecot | No fix yet | — |
Red Hat
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| RHEL 9 | dovecot +4 | 1:2.3.16-11.el9_4.1 | RHSA-2024:6529 |
| RHEL 8 | dovecot +4 | 1:2.3.16-6.el8_10 | RHSA-2024:6973 |
Show 1 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| RHEL 9.2 EUS | dovecot +4 | 1:2.3.16-8.el9_2.1 | RHSA-2024:6465 |
AlmaLinux
Errata ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| AlmaLinux 9 | dovecot +4 | 1:2.3.16-11.el9_4.1 | ALSA-2024:6529 |
| AlmaLinux 8 | dovecot +4 | 1:2.3.16-6.el8_10 | ALSA-2024:6973 |
Rocky Linux
Errata ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Rocky Linux 9 | dovecot | 1:2.3.16-11.el9_4.1 | RLSA-2024:6529 |
| Rocky Linux 8 | dovecot | 1:2.3.16-6.el8_10 | RLSA-2024:6973 |
SUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| SLES 15 SP7 | dovecot23 | 2.3.21.1-150200.76.1 | SUSE-SU-2026:4139-1 |
| SLES 15 SP6 | dovecot23 | 2.3.15-150200.65.1 | SUSE-SU-2026:4139-1, SUSE-SU-2024:3118-1 |
| SLES 15 SP5 | dovecot23 | 2.3.15-150200.65.1 | SUSE-SU-2026:4139-1, SUSE-SU-2024:3118-1 |
| SLES 15 SP4 | dovecot23 | 2.3.15-150200.65.1 | SUSE-SU-2026:4139-1, SUSE-SU-2024:3118-1 |
| SLES 15 SP3 | dovecot23 | 2.3.15-150200.65.1 | SUSE-SU-2024:3118-1 |
Show 13 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| SLES 15 SP2 | dovecot23 | 2.3.15-150200.65.1 | SUSE-SU-2024:3118-1 |
| SLES for SAP 15 SP6 | dovecot23 | 2.3.21.1-150200.76.1 | SUSE-SU-2026:4139-1 |
| SLES for SAP 15 SP5 | dovecot23 | 2.3.21.1-150200.76.1 | SUSE-SU-2026:4139-1 |
| SLES for SAP 15 SP4 | dovecot23 | 2.3.15-150200.65.1 | SUSE-SU-2026:4139-1, SUSE-SU-2024:3118-1 |
| SLES for SAP 15 SP3 | dovecot23 | 2.3.15-150200.65.1 | SUSE-SU-2024:3118-1 |
| SLES for SAP 15 SP2 | dovecot23 | 2.3.15-150200.65.1 | SUSE-SU-2024:3118-1 |
| SLE HPC 15 SP5 | dovecot23 | 2.3.21.1-150200.76.1 | SUSE-SU-2026:4139-1 |
| SLE HPC 15 SP4 | dovecot23 | 2.3.15-150200.65.1 | SUSE-SU-2026:4139-1, SUSE-SU-2024:3118-1 |
| SLE HPC 15 SP3 | dovecot23 | 2.3.15-150200.65.1 | SUSE-SU-2024:3118-1 |
| SLE HPC 15 SP2 | dovecot23 | 2.3.15-150200.65.1 | SUSE-SU-2024:3118-1 |
| SUSE Manager Server 4.3 | dovecot23 | 2.3.15-150200.65.1 | SUSE-SU-2024:3118-1 |
| SUSE Manager Proxy 4.3 | dovecot23 | 2.3.15-150200.65.1 | SUSE-SU-2024:3118-1 |
| SUSE Enterprise Storage 7.1 | dovecot23 | 2.3.15-150200.65.1 | SUSE-SU-2024:3118-1 |
openSUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| openSUSE Tumbleweed | dovecot23 | 2.3.21.1-1.1 | openSUSE-SU-2024:14274-1 |
| openSUSE Tumbleweed | dovecot24 | 2.4.0-1.1 | openSUSE-SU-2025:14715-1 |
| openSUSE Leap 15.6 | dovecot23 | 2.3.15-150200.65.1 | SUSE-SU-2024:3118-1 |
| openSUSE Leap 15.5 | dovecot23 | 2.3.15-150200.65.1 | SUSE-SU-2024:3118-1 |
Alpine
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Alpine v3.24 | dovecot | 2.3.21.1-r0 | — |
| Alpine v3.23 | dovecot | 2.3.21.1-r0 | — |
| Alpine v3.22 | dovecot | 2.3.21.1-r0 | — |
| Alpine v3.21 | dovecot | 2.3.21.1-r0 | — |
Amazon Linux
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Amazon Linux 2023 | dovecot +4 | 1:2.3.20-1.amzn2023.0.2 | ALAS2023-2024-785 |
| Amazon Linux 2 | dovecot +4 | 1:2.2.36-6.amzn2.1.2 | ALAS2-2024-2719 |
Azure Linux
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Azure Linux 3 | dovecot | No fix yet | — |
| Azure Linux 2 (CBL-Mariner) | dovecot | No fix yet | — |
Oracle Linux
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Oracle Linux 9 | dovecot +4 | 1:2.3.16-11.el9_4.1 | ELSA-2024-6529 |
| Oracle Linux 8 | dovecot +4 | 1:2.3.16-6.el8_10 | ELSA-2024-6973 |
Advisories 20
- RHSA-2024:6529 Red Hat Security Advisory: dovecot security update Red Hat Security Advisories (RHSA) · Nov 13, 2026
- ALSA-2024:6529 Moderate: dovecot security update AlmaLinux Security Advisories · Oct 29, 2026
- ALSA-2024:6973 Moderate: dovecot security update AlmaLinux Security Advisories · Oct 29, 2026
- SUSE-SU-2026:4139-1 Security update for dovecot23 SUSE / openSUSE Security Updates · Sep 28, 2026
- WID-SEC-2024-1867 Dovecot: Mehrere Schwachstellen ermöglichen Denial of Service BSI CERT-Bund (WID) · Sep 16, 2026
- RHSA-2024:6465 Red Hat Security Advisory: dovecot security update Red Hat Security Advisories (RHSA) · Jun 26, 2026
- RHSA-2024:6973 Red Hat Security Advisory: dovecot security update Red Hat Security Advisories (RHSA) · Jun 26, 2026
- USN-6982-1 dovecot vulnerabilities Ubuntu Security Notices (USN) · Apr 27, 2026
- USN-7013-1 dovecot vulnerabilities Ubuntu Security Notices (USN) · Apr 27, 2026
- DSA-5752-1 dovecot - security update Debian Security (DSA / DLA) · Mar 9, 2026
- DLA-3860-1 dovecot - security update Debian Security (DSA / DLA) · Mar 9, 2026
- RLSA-2024:6973 Moderate: dovecot security update Rocky Linux Security Advisories · Feb 5, 2026
- RLSA-2024:6529 Moderate: dovecot security update Rocky Linux Security Advisories · Feb 4, 2026
- openSUSE-SU-2025:14715-1 dovecot24-2.4.0-1.1 on GA media SUSE / openSUSE Security Updates · Feb 4, 2026
- openSUSE-SU-2024:14274-1 dovecot23-2.3.21.1-1.1 on GA media SUSE / openSUSE Security Updates · Feb 4, 2026
- SUSE-SU-2024:3118-1 Security update for dovecot23 SUSE / openSUSE Security Updates · Feb 4, 2026
- ALAS2-2024-2719 Moderate: dovecot security update (Amazon Linux 2) Amazon Linux Security Center (ALAS) · Dec 19, 2024
- ALAS2023-2024-785 Moderate: dovecot security update (Amazon Linux 2023) Amazon Linux Security Center (ALAS) · Dec 16, 2024
- ELSA-2024-6973 Moderate: dovecot security update (Oracle Linux 8) Oracle Linux Security Advisories (ELSA) · Sep 24, 2024
- ELSA-2024-6529 Moderate: dovecot security update (Oracle Linux 9) Oracle Linux Security Advisories (ELSA) · Sep 10, 2024