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    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.

    Published:Dec 6, 2021
    Last Modified:Nov 4, 2025
    EPS:Dec 6, 2021
    EPSS Score:0.00327
    CVSS Score:7.5

    Affected Products

    Vendor
    Calibre-ebook
    Product
    Calibre
    Vendor
    Fedoraproject
    Product
    Fedora

    Exploits

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

    Related CVEs

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    CVE-2026-27810 (CVSS 6.4) — calibre is a cross-platform e-book manager for viewing, converting, editing, and cataloging e-books. Prior to …
    CVE-2026-26065 (CVSS 9.3) — calibre is a cross-platform e-book manager for viewing, converting, editing, and cataloging e-books. Versions …
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    Common Vulnerability Scoring System

    Attack Vector
    Network
    Adjacent
    Local
    Physical
    Privileges Required
    None
    Low
    High
    User Interaction
    None
    Required
    Scope
    Unchanged
    Changed
    Confidentiality
    None
    Low
    High
    Integrity
    None
    Low
    High
    Availability
    None
    Low
    High