A ReDoS issue was discovered in pygments/lexers/smithy.py in pygments through 2.15.0 via SmithyLexer.

An infinite loop in SMLLexer in Pygments versions 1.5 to 2.7.3 may lead to denial of service when performing syntax highlighting of a Standard ML (SML) source file, as demonstrated by input that only contains the "exception" keyword.

In pygments 1.1+, fixed in 2.7.4, the lexers used to parse programming languages rely heavily on regular expressions. Some of the regular expressions have exponential or cubic worst-case complexity and are vulnerable to ReDoS. By crafting malicious input, an attacker can cause a denial of service.

The FontManager._get_nix_font_path function in formatters/img.py in Pygments 1.2.2 through 2.0.2 allows remote attackers to execute arbitrary commands via shell metacharacters in a font name.