{"api_version":"1","generated_at":"2026-09-13T15:19:14+00:00","cve":"CVE-2026-63073","urls":{"html":"https://cve.report/CVE-2026-63073","api":"https://cve.report/api/cve/CVE-2026-63073.json","docs":"https://cve.report/api","cve_org":"https://www.cve.org/CVERecord?id=CVE-2026-63073","nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-63073"},"summary":{"title":"Untrusted Sender DN Used as Format String in CMP Response Validation","description":"Issue summary: OpenSSL CMP response validation passed an unexpected response\nsender distinguished name directly as the format string to `ERR_raise_data()`.\n\nImpact summary: A malicious or intercepted CMP endpoint can crash a CMP client\nthat enforces an expected sender or uses a pinned server certificate whose\nsubject becomes the default expected sender.\n\nCWE: CWE-134 (Use of Externally-Controlled Format String)\n\nDescription: When validating a received CMP message, ossl_cmp_msg_check_update()\nconverts the peer-supplied sender distinguished name with X509_NAME_oneline()\nand passes it directly as the format argument to ERR_raise_data(). Percent\ncharacters survive the conversion, so a sender DN such as \"CN=%s%n\" reaches\nBIO_vsnprintf() as an attacker-controlled format string with no matching variadic\narguments. This path is only reached when the caller configures an expected\nsender or pins a server certificate, which is the normal configuration for a\nCMP client validating server responses.\n\nSince the attacker controls the format string but none of the variadic\narguments, such specifiers as %s and %n dereference or write through unrelated\nstack contents and crash the client. The reliable consequence is a denial of\nservice, when the response comes from a malicious or intercepted CMP endpoint.\nThere is no controlled memory write, arbitrary-address read, or reliable path\nto remote code execution.\n\nFIPS impact: no\n\nNo FIPS modules are affected by this issue, as the CMP protocol\nimplementation is outside the OpenSSL FIPS module boundary.","state":"PUBLISHED","assigner":"openssl","published_at":"2026-08-25 13:19:26","updated_at":"2026-09-11 21:16:45"},"problem_types":["CWE-134","CWE-134 Use of Externally-Controlled Format String"],"metrics":[{"version":"3.1","source":"ADP","type":"DECLARED","score":"9.8","severity":"CRITICAL","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","data":{"attackComplexity":"LOW","attackVector":"NETWORK","availabilityImpact":"HIGH","baseScore":9.8,"baseSeverity":"CRITICAL","confidentialityImpact":"HIGH","integrityImpact":"HIGH","privilegesRequired":"NONE","scope":"UNCHANGED","userInteraction":"NONE","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","version":"3.1"}},{"version":"3.1","source":"134c704f-9b21-4f2e-91b3-4a467353bcc0","type":"Secondary","score":"9.8","severity":"CRITICAL","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","data":{"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"}}],"references":[{"url":"https://github.com/openssl/openssl/commit/a7e5a6eea8fd3ccca6b6fbba031a5fbf8a3d93b4","name":"https://github.com/openssl/openssl/commit/a7e5a6eea8fd3ccca6b6fbba031a5fbf8a3d93b4","refsource":"openssl-security@openssl.org","tags":["Patch"],"title":"","mime":"","httpstatus":"","archivestatus":"0"},{"url":"https://openssl-library.org/news/secadv/20260825.txt","name":"https://openssl-library.org/news/secadv/20260825.txt","refsource":"openssl-security@openssl.org","tags":["Vendor 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Vulnrichment"}],"cna":{"affected":[{"defaultStatus":"unaffected","product":"OpenSSL","vendor":"OpenSSL","versions":[{"lessThan":"4.0.2","status":"affected","version":"4.0.0","versionType":"semver"},{"lessThan":"3.6.4","status":"affected","version":"3.6.0","versionType":"semver"},{"lessThan":"3.5.8","status":"affected","version":"3.5.0","versionType":"semver"},{"lessThan":"3.4.7","status":"affected","version":"3.4.0","versionType":"semver"}]}],"credits":[{"lang":"en","type":"reporter","value":"Filipe Casal (Trail of Bits)"},{"lang":"en","type":"reporter","value":"Brandon Luo"},{"lang":"en","type":"reporter","value":"TrendAI Zero Day Initiative"},{"lang":"en","type":"remediation developer","value":"Filipe Casal (Trail of Bits)"}],"datePublic":"2026-08-25T11:36:16.000Z","descriptions":[{"lang":"en","supportingMedia":[{"base64":false,"type":"text/html","value":"Issue summary: OpenSSL CMP response validation passed an unexpected response<br>sender distinguished name directly as the format string to `ERR_raise_data()`.<br><br>Impact summary: A malicious or intercepted CMP endpoint can crash a CMP client<br>that enforces an expected sender or uses a pinned server certificate whose<br>subject becomes the default expected sender.<br><br>CWE: CWE-134 (Use of Externally-Controlled Format String)<br><br>Description: When validating a received CMP message, ossl_cmp_msg_check_update()<br>converts the peer-supplied sender distinguished name with X509_NAME_oneline()<br>and passes it directly as the format argument to ERR_raise_data(). Percent<br>characters survive the conversion, so a sender DN such as \"CN=%s%n\" reaches<br>BIO_vsnprintf() as an attacker-controlled format string with no matching variadic<br>arguments. This path is only reached when the caller configures an expected<br>sender or pins a server certificate, which is the normal configuration for a<br>CMP client validating server responses.<br><br>Since the attacker controls the format string but none of the variadic<br>arguments, such specifiers as %s and %n dereference or write through unrelated<br>stack contents and crash the client. 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Percent\ncharacters survive the conversion, so a sender DN such as \"CN=%s%n\" reaches\nBIO_vsnprintf() as an attacker-controlled format string with no matching variadic\narguments. This path is only reached when the caller configures an expected\nsender or pins a server certificate, which is the normal configuration for a\nCMP client validating server responses.\n\nSince the attacker controls the format string but none of the variadic\narguments, such specifiers as %s and %n dereference or write through unrelated\nstack contents and crash the client. The reliable consequence is a denial of\nservice, when the response comes from a malicious or intercepted CMP endpoint.\nThere is no controlled memory write, arbitrary-address read, or reliable path\nto remote code execution.\n\nFIPS impact: no\n\nNo FIPS modules are affected by this issue, as the CMP protocol\nimplementation is outside the OpenSSL FIPS module boundary.","Type":"Description","Title":"Untrusted Sender DN Used as Format String in CMP Response Valida"}]}}}