Vulnerability-Lookup

CVE-2026-121577 (GCVE-0-2026-121577)

Vulnerability from cvelistv5 – Published: 2026-11-03 19:52 – Updated: 2026-11-03 19:52 X_Open Source

Title

Unescaped header separators in whatstk build a regular expression that backtracks exponentially

Summary

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.

Severity

6.7 (Medium)


                        
                          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

CWE

CWE-1333 - Inefficient Regular Expression Complexity

Assigner

Secur0 CNA under the INCIBE root

CNA scorecard A 99/100 over 46 records in the last 180 days details

References

4 references

URL	Tags
https://github.com/lucasrodes/whatstk/pull/181	patch
https://github.com/lucasrodes/whatstk/commit/01d66d8	patch
https://github.com/lucasrodes/whatstk/releases/ta…	release-notes
https://secur0.com/en/cna/cve-list/cve-2026-12157…	third-party-advisorytechnical-description

Impacted products

1 product

Vendor	Product	Version	CPE status
lucasrodes	whatstk	Affected: 0.2.0 , < 0.9.0 (semver) cpe:2.3:a:lucasrodes:whatstk::::::python::*

Credits

m.gongora.carriedo Xoán M. Otero Jorge Darío Rivas Secur0 CNA Lucas Rodés-Guirao

Show details on NVD website

JSON

To clipboard

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FKIE_CVE-2026-121577

Vulnerability from fkie_nvd - Published: 2026-11-03 20:18 - Updated: 2026-11-03 20:18

Severity

6.7 (Medium) - 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

Summary

References

	URL	Tags
	4daa8cea-433a-44bd-9456-53b127fc289a	https://github.com/lucasrodes/whatstk/commit/01d66d8
	4daa8cea-433a-44bd-9456-53b127fc289a	https://github.com/lucasrodes/whatstk/pull/181
	4daa8cea-433a-44bd-9456-53b127fc289a	https://github.com/lucasrodes/whatstk/releases/tag/v0.9.0
	4daa8cea-433a-44bd-9456-53b127fc289a	https://secur0.com/en/cna/cve-list/cve-2026-121577-whatstk-header-regex-redos

Impacted products

	Vendor	Product	Version

JSON

To clipboard

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    {
      "affectedData": [
        {
          "collectionURL": "https://pypi.org",
          "defaultStatus": "unaffected",
          "packageName": "whatstk",
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          "vendor": "lucasrodes",
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    }
  ],
  "id": "CVE-2026-121577",
  "lastModified": "2026-11-03T20:18:13.290",
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          "Recovery": "NOT_DEFINED",
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          "attackComplexity": "LOW",
          "attackRequirements": "NONE",
          "attackVector": "LOCAL",
          "availabilityRequirement": "NOT_DEFINED",
          "baseScore": 6.7,
          "baseSeverity": "MEDIUM",
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          "exploitMaturity": "NOT_DEFINED",
          "integrityRequirement": "NOT_DEFINED",
          "modifiedAttackComplexity": "NOT_DEFINED",
          "modifiedAttackRequirements": "NOT_DEFINED",
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          "modifiedPrivilegesRequired": "NOT_DEFINED",
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          "subConfidentialityImpact": "NONE",
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}

GHSA-G94X-JRVX-M3CV

Vulnerability from github – Published: 2026-11-03 21:32 – Updated: 2026-11-03 21:32

Details

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\d{1,2})+(?P\d{1,2})+(?P\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.

Severity

6.7 (Medium)


                  
                    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

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{
  "affected": [],
  "aliases": [
    "CVE-2026-121577"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-1333"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-11-03T20:18:13Z",
    "severity": "MODERATE"
  },
  "details": "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\u003cday\u003e\\d{1,2})+(?P\u003cmonth\u003e\\d{1,2})+(?P\u003cyear\u003e\\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.",
  "id": "GHSA-g94x-jrvx-m3cv",
  "modified": "2026-11-03T21:32:13Z",
  "published": "2026-11-03T21:32:13Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-121577"
    },
    {
      "type": "WEB",
      "url": "https://github.com/lucasrodes/whatstk/pull/181"
    },
    {
      "type": "WEB",
      "url": "https://github.com/lucasrodes/whatstk/commit/01d66d8"
    },
    {
      "type": "WEB",
      "url": "https://github.com/lucasrodes/whatstk/releases/tag/v0.9.0"
    },
    {
      "type": "WEB",
      "url": "https://secur0.com/en/cna/cve-list/cve-2026-121577-whatstk-header-regex-redos"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X",
      "type": "CVSS_V4"
    }
  ]
}

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The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
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CVE-2026-121577 (GCVE-0-2026-121577)

FKIE_CVE-2026-121577

GHSA-G94X-JRVX-M3CV

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