August 2024 - Dovecot-news

CVE-2024-23184: Having a large number of address headers (From, To, Cc, Bcc, etc.) becomes excessively CPU intensive
by Aki Tuomi 14 Aug '24

14 Aug '24

Affected product: Dovecot IMAP Server Internal reference: DOV-6464 Vulnerability type: CWE-770 (Allocation of Resources Without Limits or Throttling) Vulnerable version: 2.2, 2.3 Vulnerable component: lib-mail Report confidence: Confirmed Solution status: Fixed in 2.3.21.1 Researcher credits: Vendor internal discovery Vendor notification: 2024-01-30 CVE reference: CVE-2024-23184 CVSS: 5.0 (CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:L/A:N) Vulnerability Details: Having a large number of address headers (From, To, Cc, Bcc, etc.) becomes excessively CPU intensive. With 100k header lines CPU usage is already 12 seconds, and in a production environment we observed 500k header lines taking 18 minutes to parse. Since this can be triggered by external actors sending emails to a victim, this is a security issue. The main problem is that each header line's address is added to the end of a linked list. This is done by walking the whole linked list, which becomes more inefficient the more addresses there are. Workaround: One can implement restrictions on address headers on MTA component preceding Dovecot. Fix: Install non-vulnerable version of Dovecot. Patch can be found at https://github.com/dovecot/core/compare/8e4c42d%5E...1481c04.patch

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CVE-2024-23185: Very large headers can cause resource exhaustion when parsing message
by Aki Tuomi 14 Aug '24

14 Aug '24

Affected product: Dovecot IMAP Server Internal reference: DOV-6601 Vulnerability type: CWE-770 (Allocation of Resources Without Limits or Throttling) Vulnerable version: 2.2, 2.3 Vulnerable component: lib-mail Report confidence: Confirmed Solution status: Fixed in 2.3.21.1 Researcher credits: Vendor internal discovery Vendor notification: 2024-01-31 CVE reference: CVE-2024-23185 CVSS: 7.5 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H) Vulnerability Details: 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). Workaround: One can implement restrictions on headers on MTA component preceding Dovecot. Fix: Install non-vulnerable version of Dovecot. Patch can be found at https://github.com/dovecot/core/compare/f020e13%5E...ce88c33.patch

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Pigeonhole v0.5.21.1 released
by Aki Tuomi 14 Aug '24

14 Aug '24

Hi all, we are releasing new version of Pigeonhole. https://pigeonhole.dovecot.org/releases/2.3/dovecot-2.3-pigeonhole-0.5.21.1… https://pigeonhole.dovecot.org/releases/2.3/dovecot-2.3-pigeonhole-0.5.21.1… Binary packages in https://repo.dovecot.org/ Docker images in https://hub.docker.com/r/dovecot/dovecot Kind regards, Aki Tuomi Open-Xchange oy --- - sieve: When saving to local storage failed after a successful action in sieve (e.g. redirect, vacation), the mail was reported as successfully delivered, although it was lost locally.

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Dovecot v2.3.21.1 released
by Aki Tuomi 14 Aug '24

14 Aug '24

Hi all, we are releasing a CVE patch release 2.3.21.1. https://dovecot.org/releases/2.3/dovecot-2.3.21.1.tar.gz https://dovecot.org/releases/2.3/dovecot-2.3.21.1.tar.gz.sig Binary packages in https://repo.dovecot.org/ Docker images in https://hub.docker.com/r/dovecot/dovecot Kind regards, Aki Tuomi Open-Xchange oy --- - CVE-2024-23184: A large number of address headers in email resulted in excessive CPU usage. - CVE-2024-23185: Abnormally large email headers are now truncated or discarded, with a limit of 10MB on a single header and 50MB for all the headers of all the parts of an email. - oauth2: Dovecot would send client_id and client_secret as POST parameters to introspection server. These need to be optionally in Basic auth instead as required by OIDC specification. - oauth2: JWT key type check was too strict. - oauth2: JWT token audience was not validated against client_id as required by OIDC specification. - oauth2: XOAUTH2 and OAUTHBEARER mechanisms were not giving out protocol specific error message on all errors. This broke OIDC discovery. - oauth2: JWT aud validation was not performed if aud was missing from token, but was configured on Dovecot.

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