{"api_version":"1","generated_at":"2026-11-04T11:44:59+00:00","cve":"CVE-2026-121577","urls":{"html":"https://cve.report/CVE-2026-121577","api":"https://cve.report/api/cve/CVE-2026-121577.json","docs":"https://cve.report/api","cve_org":"https://www.cve.org/CVERecord?id=CVE-2026-121577","nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-121577"},"summary":{"title":"Unescaped header separators in whatstk build a regular expression that backtracks exponentially","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.","state":"PUBLISHED","assigner":"Secur0","published_at":"2026-11-03 20:18:13","updated_at":"2026-11-03 20:18:13"},"problem_types":["CWE-1333","CWE-1333 CWE-1333 Inefficient Regular Expression Complexity"],"metrics":[{"version":"4.0","source":"4daa8cea-433a-44bd-9456-53b127fc289a","type":"Secondary","score":"6.7","severity":"MEDIUM","vector":"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","data":{"version":"4.0","vectorString":"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","baseScore":6.7,"baseSeverity":"MEDIUM","attackVector":"LOCAL","attackComplexity":"LOW","attackRequirements":"NONE","privilegesRequired":"NONE","userInteraction":"ACTIVE","vulnConfidentialityImpact":"NONE","vulnIntegrityImpact":"NONE","vulnAvailabilityImpact":"HIGH","subConfidentialityImpact":"NONE","subIntegrityImpact":"NONE","subAvailabilityImpact":"NONE","exploitMaturity":"NOT_DEFINED","confidentialityRequirement":"NOT_DEFINED","integrityRequirement":"NOT_DEFINED","availabilityRequirement":"NOT_DEFINED","modifiedAttackVector":"NOT_DEFINED","modifiedAttackComplexity":"NOT_DEFINED","modifiedAttackRequirements":"NOT_DEFINED","modifiedPrivilegesRequired":"NOT_DEFINED","modifiedUserInteraction":"NOT_DEFINED","modifiedVulnConfidentialityImpact":"NOT_DEFINED","modifiedVulnIntegrityImpact":"NOT_DEFINED","modifiedVulnAvailabilityImpact":"NOT_DEFINED","modifiedSubConfidentialityImpact":"NOT_DEFINED","modifiedSubIntegrityImpact":"NOT_DEFINED","modifiedSubAvailabilityImpact":"NOT_DEFINED","Safety":"NOT_DEFINED","Automatable":"NOT_DEFINED","Recovery":"NOT_DEFINED","valueDensity":"NOT_DEFINED","vulnerabilityResponseEffort":"NOT_DEFINED","providerUrgency":"NOT_DEFINED"}},{"version":"4.0","source":"CNA","type":"CVSS","score":"6.7","severity":"MEDIUM","vector":"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","data":{"Automatable":"NOT_DEFINED","Recovery":"NOT_DEFINED","Safety":"NOT_DEFINED","attackComplexity":"LOW","attackRequirements":"NONE","attackVector":"LOCAL","baseScore":6.7,"baseSeverity":"MEDIUM","exploitMaturity":"NOT_DEFINED","privilegesRequired":"NONE","providerUrgency":"NOT_DEFINED","subAvailabilityImpact":"NONE","subConfidentialityImpact":"NONE","subIntegrityImpact":"NONE","userInteraction":"ACTIVE","valueDensity":"NOT_DEFINED","vectorString":"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","version":"4.0","vulnAvailabilityImpact":"HIGH","vulnConfidentialityImpact":"NONE","vulnIntegrityImpact":"NONE","vulnerabilityResponseEffort":"NOT_DEFINED"}}],"references":[{"url":"https://secur0.com/en/cna/cve-list/cve-2026-121577-whatstk-header-regex-redos","name":"https://secur0.com/en/cna/cve-list/cve-2026-121577-whatstk-header-regex-redos","refsource":"4daa8cea-433a-44bd-9456-53b127fc289a","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://github.com/lucasrodes/whatstk/releases/tag/v0.9.0","name":"https://github.com/lucasrodes/whatstk/releases/tag/v0.9.0","refsource":"4daa8cea-433a-44bd-9456-53b127fc289a","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://github.com/lucasrodes/whatstk/pull/181","name":"https://github.com/lucasrodes/whatstk/pull/181","refsource":"4daa8cea-433a-44bd-9456-53b127fc289a","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://github.com/lucasrodes/whatstk/commit/01d66d8","name":"https://github.com/lucasrodes/whatstk/commit/01d66d8","refsource":"4daa8cea-433a-44bd-9456-53b127fc289a","tags":[],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-121577","name":"CVE Program record","refsource":"CVE.ORG","tags":["canonical"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-121577","name":"NVD vulnerability detail","refsource":"NVD","tags":["canonical","analysis"]}],"affected":[{"source":"CNA","vendor":"lucasrodes","product":"whatstk","version":"affected 0.2.0 0.9.0 semver","platforms":[]}],"timeline":[],"solutions":[{"source":"CNA","title":"","value":"Upgrade to whatstk 0.9.0 or later.","time":"","lang":"en"}],"workarounds":[],"exploits":[],"credits":[{"source":"CNA","value":"m.gongora.carriedo","lang":"en"},{"source":"CNA","value":"Xoán M. Otero Jorge","lang":"en"},{"source":"CNA","value":"Darío Rivas","lang":"en"},{"source":"CNA","value":"Secur0 CNA","lang":"en"},{"source":"CNA","value":"Lucas Rodés-Guirao","lang":"en"}],"nvd_cpes":[],"vendor_comments":[],"enrichments":{"kev":null,"epss":null,"legacy_qids":[]},"source_records":{"cve_program":{"containers":{"cna":{"affected":[{"collectionURL":"https://pypi.org","defaultStatus":"unaffected","packageName":"whatstk","product":"whatstk","programFiles":["whatstk/whatsapp/parser.py","whatstk/whatsapp/auto_header.py"],"repo":"https://github.com/lucasrodes/whatstk","vendor":"lucasrodes","versions":[{"lessThan":"0.9.0","status":"affected","version":"0.2.0","versionType":"semver"}]}],"cpeApplicability":[{"nodes":[{"cpeMatch":[{"criteria":"cpe:2.3:a:lucasrodes:whatstk:*:*:*:*:*:python:*:*","versionEndExcluding":"0.9.0","versionStartIncluding":"0.2.0","vulnerable":true}],"negate":false,"operator":"OR"}],"operator":"OR"}],"credits":[{"lang":"en","type":"finder","value":"m.gongora.carriedo"},{"lang":"en","type":"analyst","value":"Xoán M. Otero Jorge"},{"lang":"en","type":"analyst","value":"Darío Rivas"},{"lang":"en","type":"coordinator","value":"Secur0 CNA"},{"lang":"en","type":"remediation developer","value":"Lucas Rodés-Guirao"}],"descriptions":[{"lang":"en","supportingMedia":[{"base64":false,"type":"text/html","value":"Inefficient Regular Expression Complexity (CWE-1333) in <code>generate_regex()</code> (<code>whatstk/whatsapp/parser.py</code>) 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 <code>%x</code> 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 <code>+</code> quantifies the preceding capture group, giving <code>(?P&lt;day&gt;\\d{1,2})+(?P&lt;month&gt;\\d{1,2})+(?P&lt;year&gt;\\d{2,4})</code>, 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 <code>(</code>, <code>)</code> and <code>\\</code> instead raise <code>re.PatternError</code>, separators of <code>*</code>, <code>|</code> and <code>?</code> raise <code>TypeError</code>, and separators of <code>^</code> and <code>$</code> raise <code>KeyError</code>, none of which the library catches. 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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."}],"metrics":[{"cvssV4_0":{"Automatable":"NOT_DEFINED","Recovery":"NOT_DEFINED","Safety":"NOT_DEFINED","attackComplexity":"LOW","attackRequirements":"NONE","attackVector":"LOCAL","baseScore":6.7,"baseSeverity":"MEDIUM","exploitMaturity":"NOT_DEFINED","privilegesRequired":"NONE","providerUrgency":"NOT_DEFINED","subAvailabilityImpact":"NONE","subConfidentialityImpact":"NONE","subIntegrityImpact":"NONE","userInteraction":"ACTIVE","valueDensity":"NOT_DEFINED","vectorString":"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","version":"4.0","vulnAvailabilityImpact":"HIGH","vulnConfidentialityImpact":"NONE","vulnIntegrityImpact":"NONE","vulnerabilityResponseEffort":"NOT_DEFINED"},"format":"CVSS","scenarios":[{"lang":"en","value":"GENERAL"}]}],"problemTypes":[{"descriptions":[{"cweId":"CWE-1333","description":"CWE-1333 Inefficient Regular Expression Complexity","lang":"en","type":"CWE"}]}],"providerMetadata":{"dateUpdated":"2026-11-03T19:52:54.454Z","orgId":"4daa8cea-433a-44bd-9456-53b127fc289a","shortName":"Secur0"},"references":[{"tags":["patch"],"url":"https://github.com/lucasrodes/whatstk/pull/181"},{"tags":["patch"],"url":"https://github.com/lucasrodes/whatstk/commit/01d66d8"},{"tags":["release-notes"],"url":"https://github.com/lucasrodes/whatstk/releases/tag/v0.9.0"},{"tags":["third-party-advisory","technical-description"],"url":"https://secur0.com/en/cna/cve-list/cve-2026-121577-whatstk-header-regex-redos"}],"solutions":[{"lang":"en","supportingMedia":[{"base64":false,"type":"text/html","value":"Upgrade to whatstk 0.9.0 or later."}],"value":"Upgrade to whatstk 0.9.0 or later."}],"source":{"discovery":"EXTERNAL"},"tags":["x_open-source"],"title":"Unescaped header separators in whatstk build a regular expression that backtracks exponentially","x_generator":{"engine":"Vulnogram 1.0.5"}}},"cveMetadata":{"assignerOrgId":"4daa8cea-433a-44bd-9456-53b127fc289a","assignerShortName":"Secur0","cveId":"CVE-2026-121577","datePublished":"2026-11-03T19:52:54.454Z","dateReserved":"2026-11-03T15:29:19.749Z","dateUpdated":"2026-11-03T19:52:54.454Z","state":"PUBLISHED"},"dataType":"CVE_RECORD","dataVersion":"5.2"},"nvd":{"publishedDate":"2026-11-03 20:18:13","lastModifiedDate":"2026-11-03 20:18:13","problem_types":["CWE-1333","CWE-1333 CWE-1333 Inefficient Regular Expression Complexity"],"metrics":{"cvssMetricV40":[{"source":"4daa8cea-433a-44bd-9456-53b127fc289a","type":"Secondary","cvssData":{"version":"4.0","vectorString":"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","baseScore":6.7,"baseSeverity":"MEDIUM","attackVector":"LOCAL","attackComplexity":"LOW","attackRequirements":"NONE","privilegesRequired":"NONE","userInteraction":"ACTIVE","vulnConfidentialityImpact":"NONE","vulnIntegrityImpact":"NONE","vulnAvailabilityImpact":"HIGH","subConfidentialityImpact":"NONE","subIntegrityImpact":"NONE","subAvailabilityImpact":"NONE","exploitMaturity":"NOT_DEFINED","confidentialityRequirement":"NOT_DEFINED","integrityRequirement":"NOT_DEFINED","availabilityRequirement":"NOT_DEFINED","modifiedAttackVector":"NOT_DEFINED","modifiedAttackComplexity":"NOT_DEFINED","modifiedAttackRequirements":"NOT_DEFINED","modifiedPrivilegesRequired":"NOT_DEFINED","modifiedUserInteraction":"NOT_DEFINED","modifiedVulnConfidentialityImpact":"NOT_DEFINED","modifiedVulnIntegrityImpact":"NOT_DEFINED","modifiedVulnAvailabilityImpact":"NOT_DEFINED","modifiedSubConfidentialityImpact":"NOT_DEFINED","modifiedSubIntegrityImpact":"NOT_DEFINED","modifiedSubAvailabilityImpact":"NOT_DEFINED","Safety":"NOT_DEFINED","Automatable":"NOT_DEFINED","Recovery":"NOT_DEFINED","valueDensity":"NOT_DEFINED","vulnerabilityResponseEffort":"NOT_DEFINED","providerUrgency":"NOT_DEFINED"}}]},"configurations":[]},"legacy_mitre":{"record":{"CveYear":"2026","CveId":"121577","Ordinal":"1","Title":"Unescaped header separators in whatstk build a regular expressio","CVE":"CVE-2026-121577","Year":"2026"},"notes":[{"CveYear":"2026","CveId":"121577","Ordinal":"1","NoteData":"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.","Type":"Description","Title":"Unescaped header separators in whatstk build a regular expressio"}]}}}