{"dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": {"cveId": "CVE-2026-123660", "assignerOrgId": "5a6e4751-2f3f-4070-9419-94fb35b644e8", "state": "PUBLISHED", "assignerShortName": "CIRCL", "dateReserved": "2026-11-06T08:57:03.368Z", "datePublished": "2026-11-06T08:58:24.857Z", "dateUpdated": "2026-11-06T09:04:51.732Z"}, "containers": {"cna": {"affected": [{"defaultStatus": "unaffected", "product": "vulnerability-lookup", "vendor": "vulnerability-lookup", "versions": [{"lessThan": "6.4.1", "status": "affected", "version": "5.5.1", "versionType": "semver"}]}], "credits": [{"lang": "en", "type": "reporter", "value": "Matteo Panzeri (Universit\u00e0 di Pavia), GitHub @matte1782"}, {"lang": "en", "type": "remediation developer", "value": "Claude Opus 5"}, {"lang": "en", "type": "coordinator", "value": "C\u00e9dric Bonhomme"}], "descriptions": [{"lang": "en", "supportingMedia": [{"base64": false, "type": "text/html", "value": "In Vulnerability-Lookup 5.5.1 up to but not including 6.4.1, a signed-in user could make the server allocate memory far out of proportion to their input through a webhook notification's payload template. Each placeholder's format specifier was passed unchanged to Python's string formatting, which builds the padded result before its size can be checked. A template of a few dozen bytes, such as {\"text\": \"{title:>999999999}\"}, therefore produced a string of about 1 GB when the notification form test-rendered it on save, and repeating such fields multiplied the cost. Templates that passed the save check could also repeat placeholders such as {text} thousands of times; the notification daemon rebuilt those on every webhook delivery. Deeply nested templates raised an unhandled recursion error (HTTP 500). An attacker needs only an account, which the default configuration lets anyone create after e-mail confirmation. They could exhaust the memory of web workers or the notification daemon, causing a denial of service. Version 6.4.1 caps every number in a format specifier at 256, limits a rendered template to 1,000,000 characters both on save and at delivery, and rejects templates nested deeper than 32 levels."}], "value": "In Vulnerability-Lookup 5.5.1 up to but not including 6.4.1, a signed-in user could make the server allocate memory far out of proportion to their input through a webhook notification's payload template. Each placeholder's format specifier was passed unchanged to Python's string formatting, which builds the padded result before its size can be checked. A template of a few dozen bytes, such as {\"text\": \"{title:>999999999}\"}, therefore produced a string of about 1 GB when the notification form test-rendered it on save, and repeating such fields multiplied the cost. Templates that passed the save check could also repeat placeholders such as {text} thousands of times; the notification daemon rebuilt those on every webhook delivery. Deeply nested templates raised an unhandled recursion error (HTTP 500). An attacker needs only an account, which the default configuration lets anyone create after e-mail confirmation. They could exhaust the memory of web workers or the notification daemon, causing a denial of service. Version 6.4.1 caps every number in a format specifier at 256, limits a rendered template to 1,000,000 characters both on save and at delivery, and rejects templates nested deeper than 32 levels."}], "impacts": [{"capecId": "CAPEC-130", "descriptions": [{"lang": "en", "value": "CAPEC-130 Excessive Allocation"}]}], "metrics": [{"cvssV4_0": {"Automatable": "NOT_DEFINED", "Recovery": "NOT_DEFINED", "Safety": "NOT_DEFINED", "attackComplexity": "LOW", "attackRequirements": "NONE", "attackVector": "NETWORK", "baseScore": 5.3, "baseSeverity": "MEDIUM", "privilegesRequired": "LOW", "providerUrgency": "NOT_DEFINED", "subAvailabilityImpact": "NONE", "subConfidentialityImpact": "NONE", "subIntegrityImpact": "NONE", "userInteraction": "NONE", "valueDensity": "NOT_DEFINED", "vectorString": "CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N", "version": "4.0", "vulnAvailabilityImpact": "LOW", "vulnConfidentialityImpact": "NONE", "vulnIntegrityImpact": "NONE", "vulnerabilityResponseEffort": "NOT_DEFINED"}, "format": "CVSS", "scenarios": [{"lang": "en", "value": "GENERAL"}]}], "problemTypes": [{"descriptions": [{"cweId": "CWE-770", "description": "CWE-770 Allocation of Resources Without Limits or Throttling", "lang": "en", "type": "CWE"}]}, {"descriptions": [{"cweId": "CWE-1284", "description": "CWE-1284 Improper Validation of Specified Quantity in Input", "lang": "en", "type": "CWE"}]}, {"descriptions": [{"cweId": "CWE-674", "description": "CWE-674 Uncontrolled Recursion", "lang": "en", "type": "CWE"}]}], "providerMetadata": {"orgId": "5a6e4751-2f3f-4070-9419-94fb35b644e8", "shortName": "CIRCL", "dateUpdated": "2026-11-06T09:04:51.732Z"}, "references": [{"tags": ["patch"], "url": "https://github.com/vulnerability-lookup/vulnerability-lookup/commit/2076ffdae3d024649114eeb6fd185338d4bb1f40"}], "source": {"discovery": "UNKNOWN"}, "title": "Vulnerability-Lookup: memory amplification through webhook payload template format specifiers", "x_gcve": [{"extensions": {"bcp-05-x-03": {"x_timeline": {"entities": [{"category": "discoverer", "id": "entity-reporter", "name": "Matteo Panzeri", "references": ["https://github.com/matte1782"]}, {"category": "vendor", "description": "Maintainer of Vulnerability-Lookup and operator of the vulnerability.circl.lu instance.", "id": "entity-circl", "name": "CIRCL", "references": ["https://github.com/vulnerability-lookup/vulnerability-lookup"]}], "events": [{"actor": "researcher", "actorRefs": ["entity-reporter"], "description": "Private report sent to info@circl.lu, based on a bounded local run against commit 2bb9b2f0; no request was sent to the public service.", "id": "evt-reported", "recipientRefs": ["entity-circl"], "timestamp": "2026-11-05T19:41:52Z", "type": "reported"}, {"actor": "vendor", "actorRefs": ["entity-circl"], "description": "Reproduced on the save and delivery paths; review found related amplification via repeated placeholders and an unhandled recursion error.", "id": "evt-validated", "referencedEvents": ["evt-reported"], "timestamp": "2026-11-06", "type": "validated"}, {"actor": "vendor", "actorRefs": ["entity-circl"], "id": "evt-fix-developed", "referencedEvents": ["evt-validated"], "references": ["https://github.com/vulnerability-lookup/vulnerability-lookup/commit/2076ffdae3d024649114eeb6fd185338d4bb1f40"], "timestamp": "2026-11-06T08:10:26Z", "type": "fix-developed"}, {"actor": "vendor", "actorRefs": ["entity-circl"], "description": "Vulnerability-Lookup 6.4.1 released.", "id": "evt-fix-available", "referencedEvents": ["evt-fix-developed"], "references": ["https://github.com/vulnerability-lookup/vulnerability-lookup/releases/tag/v6.4.1"], "timestamp": "2026-11-06T08:24:38Z", "type": "fix-available"}, {"actor": "vendor", "actorRefs": ["entity-circl"], "description": "Fix and changelog entry describing the issue made public with the 6.4.1 release.", "id": "evt-public-disclosure", "references": ["https://github.com/vulnerability-lookup/vulnerability-lookup/blob/v6.4.1/CHANGELOG.md"], "timestamp": "2026-11-06T08:24:38Z", "type": "public-disclosure"}, {"actor": "vendor", "actorRefs": ["entity-circl"], "description": "6.4.1 deployed on the CIRCL production instance.", "id": "evt-fix-deployed", "referencedEvents": ["evt-fix-available"], "timestamp": "2026-11-06", "type": "fix-deployed"}, {"actor": "gna", "actorRefs": ["entity-circl"], "description": "GCVE-1-2026-20054 assigned.", "id": "evt-identifier-assigned", "timestamp": "2026-11-06T08:43:51Z", "type": "identifier-assigned"}, {"actor": "gna", "actorRefs": ["entity-circl"], "id": "evt-advisory-published", "referencedEvents": ["evt-identifier-assigned"], "references": ["https://vulnerability.circl.lu/vuln/gcve-1-2026-20054"], "timestamp": "2026-11-06T08:43:51Z", "type": "advisory-published"}], "regulatory": [{"assessment": "not-applicable", "framework": "EU-CRA", "jurisdiction": "EU", "notes": "No exploitation observed; the Article 14 notification obligations for actively exploited vulnerabilities do not apply."}]}}}, "recordType": "advisory", "vulnId": "gcve-1-2026-20054"}], "x_generator": {"engine": "Vulnogram 0.2.0"}}}}

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{"affected": [{"affectedData": [{"defaultStatus": "unaffected", "product": "vulnerability-lookup", "vendor": "vulnerability-lookup", "versions": [{"lessThan": "6.4.1", "status": "affected", "version": "5.5.1", "versionType": "semver"}]}], "source": "5a6e4751-2f3f-4070-9419-94fb35b644e8"}], "cveTags": [], "descriptions": [{"lang": "en", "value": "In Vulnerability-Lookup 5.5.1 up to but not including 6.4.1, a signed-in user could make the server allocate memory far out of proportion to their input through a webhook notification's payload template. Each placeholder's format specifier was passed unchanged to Python's string formatting, which builds the padded result before its size can be checked. A template of a few dozen bytes, such as {\"text\": \"{title:>999999999}\"}, therefore produced a string of about 1 GB when the notification form test-rendered it on save, and repeating such fields multiplied the cost. Templates that passed the save check could also repeat placeholders such as {text} thousands of times; the notification daemon rebuilt those on every webhook delivery. Deeply nested templates raised an unhandled recursion error (HTTP 500). An attacker needs only an account, which the default configuration lets anyone create after e-mail confirmation. They could exhaust the memory of web workers or the notification daemon, causing a denial of service. Version 6.4.1 caps every number in a format specifier at 256, limits a rendered template to 1,000,000 characters both on save and at delivery, and rejects templates nested deeper than 32 levels."}], "id": "CVE-2026-123660", "lastModified": "2026-11-06T09:17:01.367", "metrics": {"cvssMetricV40": [{"cvssData": {"Automatable": "NOT_DEFINED", "Recovery": "NOT_DEFINED", "Safety": "NOT_DEFINED", "attackComplexity": "LOW", "attackRequirements": "NONE", "attackVector": "NETWORK", "availabilityRequirement": "NOT_DEFINED", "baseScore": 5.3, "baseSeverity": "MEDIUM", "confidentialityRequirement": "NOT_DEFINED", "exploitMaturity": "NOT_DEFINED", "integrityRequirement": "NOT_DEFINED", "modifiedAttackComplexity": "NOT_DEFINED", "modifiedAttackRequirements": "NOT_DEFINED", "modifiedAttackVector": "NOT_DEFINED", "modifiedPrivilegesRequired": "NOT_DEFINED", "modifiedSubAvailabilityImpact": "NOT_DEFINED", "modifiedSubConfidentialityImpact": "NOT_DEFINED", "modifiedSubIntegrityImpact": "NOT_DEFINED", "modifiedUserInteraction": "NOT_DEFINED", "modifiedVulnAvailabilityImpact": "NOT_DEFINED", "modifiedVulnConfidentialityImpact": "NOT_DEFINED", "modifiedVulnIntegrityImpact": "NOT_DEFINED", "privilegesRequired": "LOW", "providerUrgency": "NOT_DEFINED", "subAvailabilityImpact": "NONE", "subConfidentialityImpact": "NONE", "subIntegrityImpact": "NONE", "userInteraction": "NONE", "valueDensity": "NOT_DEFINED", "vectorString": "CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:L/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", "version": "4.0", "vulnAvailabilityImpact": "LOW", "vulnConfidentialityImpact": "NONE", "vulnIntegrityImpact": "NONE", "vulnerabilityResponseEffort": "NOT_DEFINED"}, "source": "5a6e4751-2f3f-4070-9419-94fb35b644e8", "type": "Secondary"}]}, "published": "2026-11-06T09:17:01.367", "references": [{"source": "5a6e4751-2f3f-4070-9419-94fb35b644e8", "url": "https://github.com/vulnerability-lookup/vulnerability-lookup/commit/2076ffdae3d024649114eeb6fd185338d4bb1f40"}], "sourceIdentifier": "5a6e4751-2f3f-4070-9419-94fb35b644e8", "vulnStatus": "Received", "weaknesses": [{"description": [{"lang": "en", "value": "CWE-674"}, {"lang": "en", "value": "CWE-770"}, {"lang": "en", "value": "CWE-1284"}], "source": "5a6e4751-2f3f-4070-9419-94fb35b644e8", "type": "Secondary"}]}

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