lucasrodes whatstk up to 0.8.x Header Auto Detection parser.py generate_regex redos

Summaryinfo

A vulnerability was found in lucasrodes whatstk up to 0.8.x. It has been declared as problematic. The affected element is the function generate_regex of the file whatstk/whatsapp/parser.py of the component Header Auto Detection. The manipulation results in redos. This vulnerability is known as CVE-2026-121577. It is possible to launch the attack remotely. No exploit is available. It is recommended to upgrade the affected component.

Detailsinfo

A vulnerability, which was classified as problematic, was found in lucasrodes whatstk up to 0.8.x. Affected is the function generate_regex of the file whatstk/whatsapp/parser.py of the component Header Auto Detection. The manipulation with an unknown input leads to a redos vulnerability. CWE is classifying the issue as CWE-1333. The product uses a regular expression with an inefficient, possibly exponential worst-case computational complexity that consumes excessive CPU cycles. This is going to have an impact on availability. CVE summarizes:

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.

The advisory is available at github.com. This vulnerability is traded as CVE-2026-121577 since 11/03/2026. The exploitability is told to be easy. It is possible to launch the attack remotely. Technical details are known, but there is no available exploit. This vulnerability is assigned to T1449.003 by the MITRE ATT&CK project.

Upgrading to version 0.9.0 eliminates this vulnerability.

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Productinfo

Vendor

• lucasrodes

Name

• whatstk

Version

• 0.1
• 0.2
• 0.3
• 0.4
• 0.5
• 0.6
• 0.7
• 0.8

Website

• Product: https://github.com/lucasrodes/whatstk/

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