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CVE-2026-121577— Unescaped header separators in whatstk build a regular expression that backtracks exponentially

Quick assessment

Affected
lucasrodes whatstk
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

在 项目（版本 0.2.0 至 0.9.0 之前）的 函数（位于 ）中存在低效的正则表达式复杂度漏洞（CWE-1333）。该漏洞允许提供聊天导出文件的攻击者，通过构造恶意输入，使解析该文件的进程陷入无限制的 CPU 消耗。 漏洞成因在于： 函数在构建头部正则表达式时，会将每个 占位符替换为对应的命名捕获组，但其余头部格式字符未进行转义处理。因此，若日期分隔符本身是正则表达式元字符，则会改变正则模式的行为而非按字面匹配。例如，当分隔符为 时，它会将前一个捕获组进行量词限定，生成类似 的模式。一旦遇到无法完成头部匹配的

CVSS 6.7 · Medium EPSS 0.13% · P3

Possible ATT&CK Techniques 1 AI

T1190 · Exploit Public-Facing Application

Affected Version Matrix 1

VendorProduct Version RangeStatus
lucasrodes whatstk 0.2.0< 0.9.0 affected
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I. Basic Information for CVE-2026-121577

Vulnerability Information
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Vulnerability Title
Unescaped header separators in whatstk build a regular expression that backtracks exponentially
Source: CVE Program / CVE List V5
Vulnerability Description
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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:A/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
Source: CVE Program / CVE List V5
Vulnerability Type
CWE-1333
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
lucasrodes whatstk 0.2.0 ~ 0.9.0 -

II. Public POCs for CVE-2026-121577

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III. Intelligence Information for CVE-2026-121577

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Other References for CVE-2026-121577 (4)

IV. Related Vulnerabilities

Same product: whatstk
Same vendor: lucasrodes
Same weakness: CWE-1333