A security issue has been found in Pigeonhole before version 0.5.15. The Sieve interpreter is not protected against abusive scripts that claim excessive resource usage, especially scripts using massive amounts of regexps. This means an attacker can cause a denial of service of the mail delivery system by using excessive amount of CPU and/or reaching the lmtp/lda process limits.
A security issue has been found in Pigeonhole before version 0.5.15. The Sieve interpreter is not protected against abusive scripts that claim excessive resource usage, especially scripts using massive amounts of regexps. This means an attacker can cause a denial of service of the mail delivery system by using excessive amount of CPU and/or reaching the lmtp/lda process limits.
https://dovecot.org/pipermail/dovecot-news/2021-June/000458.html https://dovecot.org/pipermail/dovecot-news/2021-June/000460.html https://github.com/dovecot/pigeonhole/commit/68505e444f91ebd784d419a8c11f1bc3fda3ceab
Workaround ========== Disabling the regex sieve extension avoids the worst problems. lmtp_user_concurrency_limit may also be helpful.
Vulmon