{"dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": {"cveId": "CVE-2026-63073", "assignerOrgId": "3a12439a-ef3a-4c79-92e6-6081a721f1e5", "state": "PUBLISHED", "assignerShortName": "openssl", "dateReserved": "2026-07-15T13:10:26.188Z", "datePublished": "2026-08-25T12:59:43.356Z", "dateUpdated": "2026-08-25T12:59:43.356Z"}, "containers": {"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. The reliable consequence is a denial of<br>service, when the response comes from a malicious or intercepted CMP endpoint.<br>There is no controlled memory write, arbitrary-address read, or reliable path<br>to remote code execution.<br><br>FIPS impact: no<br><br>No FIPS modules are affected by this issue, as the CMP protocol<br>implementation is outside the OpenSSL FIPS module boundary."}], "value": "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."}], "metrics": [{"format": "other", "other": {"content": {"text": "Low"}, "type": "https://openssl-library.org/policies/general/security-policy/"}}], "problemTypes": [{"descriptions": [{"cweId": "CWE-134", "description": "Use of Externally-Controlled Format String", "lang": "en", "type": "CWE"}]}], "providerMetadata": {"orgId": "3a12439a-ef3a-4c79-92e6-6081a721f1e5", "shortName": "openssl", "dateUpdated": "2026-08-25T12:59:43.356Z"}, "references": [{"name": "OpenSSL Advisory", "tags": ["vendor-advisory"], "url": "https://openssl-library.org/news/secadv/20260825.txt"}, {"name": "4.0.2 git commit", "tags": ["patch"], "url": "https://github.com/openssl/openssl/commit/7eb2e3ec9d1d4f35c8022fccd4b03398b3f33e21"}, {"name": "3.6.4 git commit", "tags": ["patch"], "url": "https://github.com/openssl/openssl/commit/6a0acc072b4d37a7cac1252a29c1ce1f00c5ec29"}, {"name": "3.5.8 git commit", "tags": ["patch"], "url": "https://github.com/openssl/openssl/commit/0cc20b322639919aa423e90799d9a57c3b4b76ca"}, {"name": "3.4.7 git commit", "tags": ["patch"], "url": "https://github.com/openssl/openssl/commit/a7e5a6eea8fd3ccca6b6fbba031a5fbf8a3d93b4"}], "source": {"discovery": "UNKNOWN"}, "title": "Untrusted Sender DN Used as Format String in CMP Response Validation", "x_generator": {"engine": "Vulnogram 0.2.0"}}}}

{}

{"affected": [{"affectedData": [{"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"}]}], "source": "openssl-security@openssl.org"}], "cveTags": [], "descriptions": [{"lang": "en", "value": "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."}], "id": "CVE-2026-63073", "lastModified": "2026-08-25T13:19:26.147", "metrics": {}, "published": "2026-08-25T13:19:26.147", "references": [{"source": "openssl-security@openssl.org", "url": "https://github.com/openssl/openssl/commit/0cc20b322639919aa423e90799d9a57c3b4b76ca"}, {"source": "openssl-security@openssl.org", "url": "https://github.com/openssl/openssl/commit/6a0acc072b4d37a7cac1252a29c1ce1f00c5ec29"}, {"source": "openssl-security@openssl.org", "url": "https://github.com/openssl/openssl/commit/7eb2e3ec9d1d4f35c8022fccd4b03398b3f33e21"}, {"source": "openssl-security@openssl.org", "url": "https://github.com/openssl/openssl/commit/a7e5a6eea8fd3ccca6b6fbba031a5fbf8a3d93b4"}, {"source": "openssl-security@openssl.org", "url": "https://openssl-library.org/news/secadv/20260825.txt"}], "sourceIdentifier": "openssl-security@openssl.org", "vulnStatus": "Received", "weaknesses": [{"description": [{"lang": "en", "value": "CWE-134"}], "source": "openssl-security@openssl.org", "type": "Secondary"}]}

{}

{"affected": [{"configurations": [{"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "[4.0.0,4.0.2)"}}, {"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "[3.6.0,3.6.4)"}}, {"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "[3.5.0,3.5.8)"}}, {"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "[3.4.0,3.4.7)"}}], "enrichment": {"confidence": 100.0, "confidence_source": "matching", "scores": [{"score": 100.0, "source": "matching"}]}, "original": {"product": "OpenSSL", "source": "cna", "vendor": "OpenSSL"}, "product": "openssl", "vendor": "openssl"}], "created": "2026-08-25T14:45:03.808280+00:00", "updated": "2026-08-25T15:00:13.907912+00:00", "vendors": ["openssl", "openssl$PRODUCT$openssl"]}