Live › vulnerability › CVE-2026-121577
whatstk is a Python library that parses WhatsApp chat exports. A crafted export with a regex metacharacter in its date separator makes the header regular expression catastrophically backtrack, so parsing consumes CPU without finishing, and some separators raise uncaught exceptions that can crash the calling program.
Summary written from the sources below. Check the originals before acting.
First seen by InfraStack 2026-11-03 20:49 UTC. All times on this page are UTC.
Only programs that parse WhatsApp chat exports supplied by someone else with whatstk from 0.2.0 before 0.9.0, with header auto detection on (the default). The separator is read from the file itself, so an attacker only needs to supply an export file; no account or special setup is described.
No product ranges from the sources yet.
pip show whatstk or the version in your pyproject.toml/requirements.txt; affected range is 0.2.0 up to but not including 0.9.0.whatstk.whatsapp.parser).0.9.0Each row is the first time that source carried this signal. The analyst’s rows are its own findings.
Inefficient Regular Expression Complexity (CWE-1333) in generate_regex() (whatstk/whatsapp/parser.py) in whatstk from 0.2.0 before 0.9.0 allows a party that supplies a chat export to consume the CPU of the process that parses it for an unbounded time, because the function builds the header regular expression by replacing each %x code with its named capture group and leaves every other character of the header format in the pattern unescaped. A header whose date separator is a regular expression metacharacter therefore alters the pattern instead of matching itself: a separator of + quantifies the preceding capture group, giving (?P<day>\d{1,2})+(?P<month>\d{1,2})+(?P<year>\d{2,4}), and a run of digits that cannot complete the header then makes the engine try every way of partitioning that run. Header auto detection is enabled by default and derives the format from the text of the file, so the separator is taken from the export itself and no header format has to be passed by the caller. Separators of (, ) and \ instead raise re.PatternError, separators of *, | and ? raise TypeError, and separators of ^ and $ raise KeyError, none of which the library catches. This results in the parse of a file of a few hundred bytes consuming CPU without completing, or in an uncaught exception in the calling program.
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