CVE-2021-44686

HIGH 7.5CVE-2021-44686 · Published 07/12/2021 · updated 17/06/2026

In short

CVE-2021-44686 is a HIGH (CVSS 7.5) vulnerability affecting calibre (calibre-ebook).
Chance of exploitation in the next 30 days (EPSS): 5.2%, higher than 92.5% of all vulnerabilities.
Fix: update to 5.32.0 or later.

Package	Affected versions	Patched versions
calibre calibre-ebook	`< 5.32.0`	`5.32.0`

Description

calibre before 5.32.0 contains a regular expression that is vulnerable to ReDoS (Regular Expression Denial of Service) in html_preprocess_rules in ebooks/conversion/preprocess.py.

References

bugs.launchpad.net/calibre/+bug/1951979 · Exploit
dwisiswant0/advisory · Exploit
kovidgoyal/calibre · Patch
lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/W7QKFPYJ23KG6WJ5NIYAM4N2NWZCLQGL
lists.debian.org/debian-lts-announce/2024/09/msg00005.html

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Package

Affected versions

Patched versions

calibre

calibre-ebook

< 5.32.0

5.32.0

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