PyMdown Extensions is a set of extensions for the Python-Markdown markdown project. Versions prior to 10.16.1 have a ReDOS bug found within the figure caption extension (pymdownx.blocks.caption). In systems that take unchecked user content, this could cause long hanges when processing the data if a malicious payload was crafted. This issue is patched in Release 10.16.1. As a workaround, those who process unknown user content without timeouts or other safeguards in place to prevent really large, malicious content being aimed at systems may avoid the use of pymdownx.blocks.caption until theyre able to upgrade.
The product uses a regular expression with an inefficient, possibly exponential worst-case computational complexity that consumes excessive CPU cycles.
Attackers can create crafted inputs that
intentionally cause the regular expression to use
excessive backtracking in a way that causes the CPU
consumption to spike.