undocumented changed behavior of 2.4.3 (possible bug report)
Hello Dovecot-Devs, hello list,
while upgrading my Dovecot 2.4.2 setup to 2.4.3 I observed two instances of changed behavior. I could not find notes about those issues in the corresponding documentation (https://doc.dovecot.org/2.4.3/installation/upgrade/2.4-to-2.4.x.html) or release notes:
- I had to change
userdb_ldap_iterate_filter = (&(objectClass=posixAccount)%{if(protocol,"eq","pop3","(istIsMemberOf=POP3-users)","")}) to userdb_ldap_iterate_filter = (&(objectClass=posixAccount)%{if(protocol,"eq","pop3","(istIsMemberOf=POP3-users)","")|safe)
otherwise the characters '()=' in the "true"-case of the condition got somehow "quoted" with escaped ASCII codes, which led to a broken LDAP filter string.
Maybe you could add some documentation (in "Upgrading" as well as "Settings Variables") about that?
- The behavior of sieve matches using ":matches" has changed:
Example email (only the relevant header): List-Id: Dovecot Mailing List <dovecot.dovecot.org>
Example Sieve script: if header :matches "List-Id" "*<dovecot*.dovecot.org>" { fileinto "dovecot"; }
In 2.4.2 (and earlier) the example email matched the condition and got stored in the dovecot folder, while in 2.4.3 the condition does NOT match. As a workaround I added a '*' at the end of the match ("*<dovecot*.dovecot.org>*") to get my mails stored correctly again.
Is this changed behavior for Sieve intentional or a bug? In case of a bug, could you please provide a fix?
In case of intentional behavior:
- Could you please explain the intention? Why was it necessary?
- What would be the correct fix for the sieve example to match a List-Id header that ENDS WITH ".dovecot.org>"?
- I assume, that other users on my servers will run into similar problems once I upgrade their servers. Is it possible to detect such problematic matches in Sieve scripts? E.g. "all matches without a trailing '*' are affected", ... This would give me a chance, to inform my users or even fix their scripts in advance.
Best regards,
Patrick Cernko <pcernko@mpi-klsb.mpg.de> +49 681 9325 5815 Joint Scientific IT and Technical Service Max-Planck-Institute für Informatik & Softwaresysteme
For one, it's documented:
https://doc.dovecot.org/2.4.3/core/config/auth/databases/ldap.html#ldap_base
this is to avoid LDAP injection attack on authentication, CVE-2026-27860
But you're right, it should've been in the 2.4.x page.
The matches change we have to check, matching was changed due to certain patterns causing assert crashes.
Aki
On 21/04/2026 14:37 EEST Patrick Cernko via dovecot <dovecot@dovecot.org> wrote:
Hello Dovecot-Devs, hello list,
while upgrading my Dovecot 2.4.2 setup to 2.4.3 I observed two instances of changed behavior. I could not find notes about those issues in the corresponding documentation (https://doc.dovecot.org/2.4.3/installation/upgrade/2.4-to-2.4.x.html) or release notes:
- I had to change
userdb_ldap_iterate_filter = (&(objectClass=posixAccount)%{if(protocol,"eq","pop3","(istIsMemberOf=POP3-users)","")}) to userdb_ldap_iterate_filter = (&(objectClass=posixAccount)%{if(protocol,"eq","pop3","(istIsMemberOf=POP3-users)","")|safe)
otherwise the characters '()=' in the "true"-case of the condition got somehow "quoted" with escaped ASCII codes, which led to a broken LDAP filter string.
Maybe you could add some documentation (in "Upgrading" as well as "Settings Variables") about that?
- The behavior of sieve matches using ":matches" has changed:
Example email (only the relevant header): List-Id: Dovecot Mailing List <dovecot.dovecot.org>
Example Sieve script: if header :matches "List-Id" "*<dovecot*.dovecot.org>" { fileinto "dovecot"; }
In 2.4.2 (and earlier) the example email matched the condition and got stored in the dovecot folder, while in 2.4.3 the condition does NOT match. As a workaround I added a '*' at the end of the match ("*<dovecot*.dovecot.org>*") to get my mails stored correctly again.
Is this changed behavior for Sieve intentional or a bug? In case of a bug, could you please provide a fix?
In case of intentional behavior:
- Could you please explain the intention? Why was it necessary?
- What would be the correct fix for the sieve example to match a List-Id header that ENDS WITH ".dovecot.org>"?
- I assume, that other users on my servers will run into similar problems once I upgrade their servers. Is it possible to detect such problematic matches in Sieve scripts? E.g. "all matches without a trailing '*' are affected", ... This would give me a chance, to inform my users or even fix their scripts in advance.
Best regards,
Patrick Cernko <pcernko@mpi-klsb.mpg.de> +49 681 9325 5815 Joint Scientific IT and Technical Service Max-Planck-Institute für Informatik & Softwaresysteme
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Hi Aki,
thanks for the fast response!
On 2026-04-21 13:46:49, Aki Tuomi via dovecot wrote:
For one, it's documented:
https://doc.dovecot.org/2.4.3/core/config/auth/databases/ldap.html#ldap_base
this is to avoid LDAP injection attack on authentication, CVE-2026-27860
But you're right, it should've been in the 2.4.x page.
ah, I missed to check ldap_base and only checked the *_filter directives' docs. Maybe add that "| safe" note for the *_filter directives too?
Best regards,
Patrick Cernko <pcernko@mpi-klsb.mpg.de> +49 681 9325 5815 Joint Scientific IT and Technical Service Max-Planck-Institute für Informatik & Softwaresysteme
Hi List, Hi Aki,
On 2026-04-21 13:46:49, Aki Tuomi via dovecot wrote:
For one, it's documented:
https://doc.dovecot.org/2.4.3/core/config/auth/databases/ldap.html#ldap_base
this is to avoid LDAP injection attack on authentication, CVE-2026-27860
But you're right, it should've been in the 2.4.x page.
The matches change we have to check, matching was changed due to certain patterns causing assert crashes.
Aki
On 21/04/2026 14:37 EEST Patrick Cernko via dovecot <dovecot@dovecot.org> wrote:
- The behavior of sieve matches using ":matches" has changed:
Example email (only the relevant header): List-Id: Dovecot Mailing List <dovecot.dovecot.org>
Example Sieve script: if header :matches "List-Id" "*<dovecot*.dovecot.org>" { fileinto "dovecot"; }
In 2.4.2 (and earlier) the example email matched the condition and got stored in the dovecot folder, while in 2.4.3 the condition does NOT match. As a workaround I added a '*' at the end of the match ("*<dovecot*.dovecot.org>*") to get my mails stored correctly again.
Is this changed behavior for Sieve intentional or a bug? In case of a bug, could you please provide a fix?
In case of intentional behavior:
- Could you please explain the intention? Why was it necessary?
- What would be the correct fix for the sieve example to match a List-Id header that ENDS WITH ".dovecot.org>"?
- I assume, that other users on my servers will run into similar problems once I upgrade their servers. Is it possible to detect such problematic matches in Sieve scripts? E.g. "all matches without a trailing '*' are affected", ... This would give me a chance, to inform my users or even fix their scripts in advance.
for the record: The mentioned changed behavior of sieve matches has been reverted in 2.4.4, as mentioned in the changelogs:
- lib-sieve: matches - Fix trailing literal match when it fills value exactly. v2.4.3 regression.
At least my specific case now works as before 2.4.3 again.
Thank you for the fix!
Patrick Cernko <pcernko@mpi-klsb.mpg.de> +49 681 9325 5815 Joint Scientific IT and Technical Service Max-Planck-Institute für Informatik & Softwaresysteme
participants (2)
-
Aki Tuomi
-
Patrick Cernko