Description
libs/comverp.c in Courier MTA before 0.53.2 allows attackers to cause a denial of service (CPU consumption) via unknown vectors involving usernames that contain the "=" (equals) character, which is not properly handled during encoding.
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 ↗Advisories 1
- DSA-1101 courier - programming error Debian Security (DSA / DLA) · Mar 9, 2026
References
- http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=368834
- courier-usernames-dos(26998) vdb-entry
- GLSA-200608-06 vendor-advisory
- 18345 vdb-entry
- 20548 third-party-advisory
- 20519 third-party-advisory
- http://www.courier-mta.org/beta/patches/verp-fix/README.txt
- 21350 third-party-advisory
- DSA-1101 vendor-advisory
- ADV-2006-2214 vdb-entry
- USN-294-1 vendor-advisory
- 20792 third-party-advisory
- 1016248 vdb-entry