CVE-2009-1391: Off-by-one error in the inflate function in Zlib.xs in Compress::Raw::Zlib Perl module before 2.017, as use...

Security readout for executives and security teams

This flaw affects older Perl zlib decompression code used by mail-filtering tools. A malicious compressed stream can make affected services hang or crash, disrupting email security processing. Sources say it was exploited in the wild in June 2009, but they do not establish current active exploitation. Exposure is most likely in legacy servers, appliances, or distributions still carrying Compress::Raw::Zlib versions before 2.017, especially mail gateways using AMaViS or SpamAssassin. Modern maintained packages are less likely exposed, but embedded or frozen Perl stacks should be checked. Treat this as a legacy exposure cleanup item unless affected mail security infrastructure is confirmed. Prioritize internet-facing mail gateways and high-volume scanning systems because failure can interrupt email filtering and business mail flow. Mitigation focus: Upgrade Compress::Raw::Zlib to version 2.017 or later where vendor packages support it.; Apply relevant operating system vendor updates for affected Perl compression packages.; Check AMaViS and SpamAssassin hosts for bundled or pinned vulnerable Perl modules..

Prepared

Jun 28, 2026, 10:45 UTC (UTC+00:00)

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.