CVE-2026-33753

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{"affected": [{"affectedData": [{"product": "rfc3161-client", "vendor": "trailofbits", "versions": [{"status": "affected", "version": "< 1.0.6"}]}], "source": "security-advisories@github.com"}], "configurations": [{"nodes": [{"cpeMatch": [{"criteria": "cpe:2.3:a:trailofbits:rfc3161-client:*:*:*:*:*:*:*:*", "matchCriteriaId": "16E3C452-B9EE-490C-A46E-F8F8B8BB936A", "versionEndExcluding": "1.0.6", "vulnerable": true}], "negate": false, "operator": "OR"}]}], "cveTags": [], "descriptions": [{"lang": "en", "value": "rfc3161-client is a Python library implementing the Time-Stamp Protocol (TSP) described in RFC 3161. Prior to 1.0.6, an Authorization Bypass vulnerability in rfc3161-client's signature verification allows any attacker to impersonate a trusted TimeStamping Authority (TSA). By exploiting a logic flaw in how the library extracts the leaf certificate from an unordered PKCS#7 bag of certificates, an attacker can append a spoofed certificate matching the target common_name and Extended Key Usage (EKU) requirements. This tricks the library into verifying these authorization rules against the forged certificate while validating the cryptographic signature against an actual trusted TSA (such as FreeTSA), thereby bypassing the intended TSA authorization pinning entirely. This vulnerability is fixed in 1.0.6."}, {"lang": "es", "value": "rfc3161-client es una biblioteca Python que implementa el Protocolo de Sellado de Tiempo (TSP) descrito en la RFC 3161. Antes de la versi\u00f3n 1.0.6, una vulnerabilidad de omisi\u00f3n de autorizaci\u00f3n en la verificaci\u00f3n de firma de rfc3161-client permite a cualquier atacante suplantar a una Autoridad de Sellado de Tiempo (TSA) de confianza. Al explotar un fallo l\u00f3gico en c\u00f3mo la biblioteca extrae el certificado hoja de una bolsa de certificados PKCS#7 desordenada, un atacante puede a\u00f1adir un certificado falsificado que coincida con los requisitos de common_name y Uso Extendido de Clave (EKU) del objetivo. Esto enga\u00f1a a la biblioteca para que verifique estas reglas de autorizaci\u00f3n contra el certificado falsificado mientras valida la firma criptogr\u00e1fica contra una TSA de confianza real (como FreeTSA), eludiendo as\u00ed por completo el anclaje de autorizaci\u00f3n de TSA previsto. Esta vulnerabilidad est\u00e1 corregida en la versi\u00f3n 1.0.6."}], "id": "CVE-2026-33753", "lastModified": "2026-07-24T23:10:00.563", "metrics": {"cvssMetricV31": [{"cvssData": {"attackComplexity": "LOW", "attackVector": "LOCAL", "availabilityImpact": "NONE", "baseScore": 6.2, "baseSeverity": "MEDIUM", "confidentialityImpact": "NONE", "integrityImpact": "HIGH", "privilegesRequired": "NONE", "scope": "UNCHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N", "version": "3.1"}, "exploitabilityScore": 2.5, "impactScore": 3.6, "source": "security-advisories@github.com", "type": "Secondary"}, {"cvssData": {"attackComplexity": "LOW", "attackVector": "NETWORK", "availabilityImpact": "NONE", "baseScore": 7.5, "baseSeverity": "HIGH", "confidentialityImpact": "NONE", "integrityImpact": "HIGH", "privilegesRequired": "NONE", "scope": "UNCHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N", "version": "3.1"}, "exploitabilityScore": 3.9, "impactScore": 3.6, "source": "nvd@nist.gov", "type": "Primary"}], "ssvcV203": [{"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "ssvcData": {"id": "CVE-2026-33753", "options": [{"exploitation": "poc"}, {"automatable": "no"}, {"technicalImpact": "partial"}], "role": "CISA Coordinator", "timestamp": "2026-04-08T16:08:28.007589Z", "version": "2.0.3"}}]}, "published": "2026-04-08T16:16:23.670", "references": [{"source": "security-advisories@github.com", "tags": ["Exploit", "Vendor Advisory"], "url": "https://github.com/trailofbits/rfc3161-client/security/advisories/GHSA-3xxc-pwj6-jgrj"}, {"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "tags": ["Exploit", "Vendor Advisory"], "url": "https://github.com/trailofbits/rfc3161-client/security/advisories/GHSA-3xxc-pwj6-jgrj"}], "sourceIdentifier": "security-advisories@github.com", "vulnStatus": "Analyzed", "weaknesses": [{"description": [{"lang": "en", "value": "CWE-295"}], "source": "security-advisories@github.com", "type": "Secondary"}]}

{"bugzilla": {"description": "rfc3161-client: rfc3161-client: Authorization bypass allows impersonation of TimeStamping Authority", "id": "2456545", "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2456545"}, "csaw": false, "cvss3": {"cvss3_base_score": "6.2", "cvss3_scoring_vector": "CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N", "status": "draft"}, "cwe": "CWE-295", "details": ["A flaw was found in rfc3161-client, a Python library implementing the Time-Stamp Protocol (TSP). This authorization bypass vulnerability allows a remote attacker to impersonate a trusted TimeStamping Authority (TSA). The flaw exists in the library's signature verification process, specifically in how it extracts certificates from a PKCS#7 bag (a standard for cryptographic messages). An attacker can exploit a logic error to present a forged certificate, leading the library to incorrectly validate authorization rules and bypass intended TSA authorization pinning."], "mitigation": {"lang": "en:us", "value": "Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability."}, "name": "CVE-2026-33753", "package_state": [{"cpe": "cpe:/a:redhat:trusted_artifact_signer:1", "fix_state": "Fix deferred", "package_name": "securesign/model-transparency", "product_name": "Red Hat Trusted Artifact Signer"}], "public_date": "2026-04-08T14:54:59Z", "references": ["https://www.cve.org/CVERecord?id=CVE-2026-33753\nhttps://nvd.nist.gov/vuln/detail/CVE-2026-33753\nhttps://github.com/trailofbits/rfc3161-client/security/advisories/GHSA-3xxc-pwj6-jgrj"], "statement": "This vulnerability has a Moderate impact. A flaw in the rfc3161-client library, used by Red Hat Trusted Artifact Signer, allows an attacker to bypass authorization and impersonate a trusted TimeStamping Authority. This is due to a logic error in how the library extracts certificates during signature verification, enabling the use of a forged certificate to bypass TSA authorization pinning. As a consequence of a successful attack applications relying in `rfc3161-client` to validate the origin of a timestamp are exposed to impersonation, causing a high impact in the integrity of the data related to the validation.", "threat_severity": "Moderate"}

{"affected": [{"configurations": [{"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "[0,1.0.6)"}}], "enrichment": {"confidence": 100.0, "confidence_source": "cna", "scores": [{"score": 100.0, "source": "cna"}]}, "original": {"product": "rfc3161-client", "source": "cna", "vendor": "trailofbits"}, "product": "rfc3161-client", "vendor": "trailofbits"}], "analysis": {"en": {"generated_at": "2026-04-08T16:20:31.374227+00:00", "value": {"mitigation_remediation": ["Upgrade rfc3161-client to version 1.0.6 or newer"], "summary": {"action": "Immediate Patch", "impact": "TSA impersonation via authorization bypass"}, "threat_synthesis": {"affected_systems": "The vulnerability affects the rfc3161-client library distributed by trailofbits. Any installation of rfc3161-client prior to version 1.0.6 is susceptible. No additional product or version specifics are provided beyond the 1.0.6 release threshold.", "description_and_impact": "A logic flaw in rfc3161-client's extraction of the leaf certificate from an unordered PKCS#7 bag allows an attacker to forge a certificate that matches the required common name and Extended Key Usage attributes. The library then verifies the authorization rules against the forged certificate while still validating the cryptographic signature against a legitimate trusted TimeStamping Authority. This bypasses the intended TSA authorization pinning and enables an attacker to impersonate a trusted TSA, potentially creating or claiming forged timestamps.", "risk_and_exploitability": "With a CVSS score of 6.2 the weakness presents a moderate severity risk. EPSS data is not available and the vulnerability is not listed in the CISA KEV catalog, indicating a lower public exploitation footprint. The attack likely requires control over the PKCS#7 signature input, allowing an attacker to inject a crafted certificate chain that satisfies the TSA verification logic. Once the forged certificate is accepted, an attacker can forge timestamps that appear valid to downstream consumers of the timestamp service."}}}}, "created": "2026-04-08T19:26:51.215205+00:00", "updated": "2026-04-08T19:39:09.083094+00:00", "vendors": ["trailofbits", "trailofbits$PRODUCT$rfc3161-client"]}