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 7.5 HIGH
CVSS v2.0 5.0 MEDIUM

7.5^/10

CVSS v3 : HIGH

Vector :

Exploitability : 3.9 / Impact : 3.6

Attack Vector NETWORK

Attack Complexity LOW

Privileges Required NONE

User Interaction NONE

Confidentiality Impact NONE

Integrity Impact NONE

Availability Impact HIGH

Scope UNCHANGED

5.0^/10

CVSS v2.0 : MEDIUM

Vector : AV:N/AC:L/Au:N/C:N/I:N/A:P

Exploitability : 10.0 / Impact : 2.9

Access Vector NETWORK

Access Complexity LOW

Authentication NONE

Confidentiality Impact NONE

Integrity Impact NONE

Availability Impact PARTIAL

References

Link	Resource
https://bugs.launchpad.net/calibre/+bug/1951979	Exploit Issue Tracking Vendor Advisory
https://github.com/dwisiswant0/advisory/issues/18	Exploit Issue Tracking Patch Third Party Advisory
https://github.com/kovidgoyal/calibre/compare/v5.31.1...v5.32.0	Patch Third Party Advisory
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/W7QKFPYJ23KG6WJ5NIYAM4N2NWZCLQGL/
https://bugs.launchpad.net/calibre/+bug/1951979	Exploit Issue Tracking Vendor Advisory
https://github.com/dwisiswant0/advisory/issues/18	Exploit Issue Tracking Patch Third Party Advisory
https://github.com/kovidgoyal/calibre/compare/v5.31.1...v5.32.0	Patch Third Party Advisory
https://lists.debian.org/debian-lts-announce/2024/09/msg00005.html
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/W7QKFPYJ23KG6WJ5NIYAM4N2NWZCLQGL/

Configurations

Configuration 1 (hide)

cpe:2.3:a:calibre-ebook:calibre:*:*:*:*:*:*:*:*

Configuration 2 (hide)

cpe:2.3:o:fedoraproject:fedora:34:*:*:*:*:*:*:*

History

04 Nov 2025, 16:15

Type	Values Removed	Values Added
References		() https://lists.debian.org/debian-lts-announce/2024/09/msg00005.html -

Information

Published : 2021-12-07 00:15

Updated : 2025-11-04 16:15

NVD link : CVE-2021-44686

Mitre link : CVE-2021-44686

CVE.ORG link : CVE-2021-44686

JSON object : View

Products Affected

calibre-ebook

calibre

fedoraproject

fedora

CWE

CWE-400

Uncontrolled Resource Consumption

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