MIME::Words versions before 5.521 for Perl allow memory exhaustion via repeated "=?" sequences in decode_mimewords.

For each "=?" that does not start a complete encoded word, decode_mimewords appends an error message containing the whole input string to $@. A boundary of 8,000 "=?" pairs (16,000 bytes) adds 8,000 copies of itself to $@, about 128 MB.

From version 5.518, MIME::Parser decodes every multipart boundary this way, so a remote sender can exhaust the memory of the parsing process with one Content-Type header.

MIME::Words versions before 5.521 for Perl allow memory exhaustion via repeated "=?" sequences in decode_mimewords.

For each "=?" that does not start a complete encoded word, decode_mimewords appends an error message containing the whole input string to $@. A boundary of 8,000 "=?" pairs (16,000 bytes) adds 8,000 copies of itself to $@, about 128 MB.

From version 5.518, MIME::Parser decodes every multipart boundary this way, so a remote sender can exhaust the memory of the parsing process with one Content-Type header.

Affected: Ubuntu:14.04:LTS: libmime-tools-perl, Ubuntu:16.04:LTS: libmime-tools-perl, Ubuntu:18.04:LTS: libmime-tools-perl, Ubuntu:20.04:LTS: libmime-tools-perl, Ubuntu:22.04:LTS: libmime-tools-perl, Ubuntu:24.04:LTS: libmime-tools-perl, Ubuntu:26.10: libmime-tools-perl, Ubuntu:26.04:LTS: libmime-tools-perl

[Unknown description]