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Disclaimer: Community trackers are created by Red Hat Product Security team on a best effort basis. Package maintainers are required to ascertain if the flaw indeed affects their package, before starting the update process. Mistune before 3.3.0 contains an algorithmic complexity vulnerability in the inline link parser that allows unauthenticated attackers to exhaust CPU by submitting long runs of unmatched '[' characters. Attackers can send small markdown payloads that trigger O(N^2) parse_link_text and parse_link_label probing, occupying rendering workers for 30+ seconds per 16 KB input.
FEDORA-2026-340793a2f1 (python-mistune-3.3.4-1.fc43) has been submitted as an update to Fedora 43. https://bodhi.fedoraproject.org/updates/FEDORA-2026-340793a2f1
FEDORA-2026-340793a2f1 has been pushed to the Fedora 43 testing repository. Soon you'll be able to install the update with the following command: `sudo dnf upgrade --enablerepo=updates-testing --refresh --advisory=FEDORA-2026-340793a2f1` You can provide feedback for this update here: https://bodhi.fedoraproject.org/updates/FEDORA-2026-340793a2f1 See also https://fedoraproject.org/wiki/QA:Updates_Testing for more information on how to test updates.