Sisimai: Mail Analyzing Interface

Release Notes

Sisimai 4.25.18

2026/08/31

Sisimai 4.25.18 is now available. The main changes in this release are fixes for a ReDoS vulnerability in the Perl and Ruby versions.

Sisimai 4 series is now in a state where it only receives fixes for critical bugs that cause overall crashes and updates to accommodate major service changes. Therefore, we recommend upgrading to Sisimai 5 series, which addresses modern delivery errors such as domain authentication and reputation.

And then, Sisimai 5 includes many changes that are not compatible with Version 4, so please check the Perl or Ruby version of your environment before installing or upgrading.

Changes

  • Perl Ruby Fixed a vulnerability where processing a bounce mail with a specially crafted HTML part through the to_plain method of Sisimai::String resulted in significantly increased processing time and 100% CPU utilization. The Go version of Sisimai is not affected by this vulnerability as it does not use regular expressions for this process. This vulnerability affects all Sisimai versions 4.25.17 and earlier.