CVE-2021-44686

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.

CVSS v3.1

7.5 HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS v2.0

5.0 MEDIUMAV:N/AC:L/Au:N/C:N/I:N/A:P

EPSS

4.99% chance of exploitation in the next 30 days, 92th percentile

Published

2021-12-06

Updated

2025-11-04

Proof-of-concept exploits (2)

• https://bugs.launchpad.net/calibre/+bug/1951979
• dwisiswant0/advisory/issues/18

References

• CVE Record
• NVD entry

Related

• CVE-2018-7600
• CVE-2020-24148
• CVE-2020-5902
• CVE-2020-9496
• CVE-2021-44684
• CVE-2021-44685