{
  "cveId": "CVE-2026-63073",
  "url": "https://patchblox.com/security/cve/CVE-2026-63073",
  "summary": "CVE-2026-63073 is fixed in 14 products on 1 platform, first by libssl3t64 3.5.5-1ubuntu3.4, released August 24, 2026. It is not reported as exploited. Patch Radar priority: High.",
  "title": "Untrusted Sender DN Used as Format String in CMP Response Validation",
  "description": "Issue summary: OpenSSL CMP response validation passed an unexpected response sender distinguished name directly as the format string to \u0060ERR_raise_data()\u0060.  Impact summary: A malicious or intercepted CMP endpoint can crash a CMP client that enforces an expected sender or uses a pinned server certificate whose subject becomes the default expected sender.  CWE: CWE-134 (Use of Externally-Controlled Format String)  Description: When validating a received CMP message, ossl_cmp_msg_check_update() converts the peer-supplied sender distinguished name with X509_NAME_oneline() and passes it directly as the format argument to ERR_raise_data(). Percent characters survive the conversion, so a sender DN such as \u0022CN=%s%n\u0022 reaches BIO_vsnprintf() as an attacker-controlled format string with no matching variadic arguments. This path is only reached when the caller configures an expected sender or pins a server certificate, which is the normal configuration for a CMP client validating server responses.  Since the attacker controls the format string but none of the variadic arguments, such specifiers as %s and %n dereference or write through unrelated stack contents and crash the client. The reliable consequence is a denial of service, when the response comes from a malicious or intercepted CMP endpoint. There is no controlled memory write, arbitrary-address read, or reliable path to remote code execution.  FIPS impact: no  No FIPS modules are affected by this issue, as the CMP protocol implementation is outside the OpenSSL FIPS module boundary.",
  "published": "2026-08-24T17:00:00Z",
  "severity": "Moderate",
  "cvss": 9.8,
  "cvssVector": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
  "cwe": "Use of Externally-Controlled Format String",
  "epss": 0.01159,
  "epssPercentile": 0.67321,
  "priority": "High",
  "priorityTier": 3,
  "exploited": false,
  "vendorExploited": false,
  "disclosed": false,
  "vendorAdvisory": "https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-63073",
  "fixes": [
    {
      "platform": "linux",
      "product": "libssl3t64",
      "release": "Ubuntu 26.04.1 LTS (resolute)",
      "fixedVersion": "3.5.5-1ubuntu3.4",
      "fix": "libssl3t64 3.5.5-1ubuntu3.4",
      "url": "https://patchblox.com/security/fix/linux/ubuntu-resolute-libssl3t64-3.5.5-1ubuntu3.4",
      "released": "2026-08-24T17:00:00Z"
    },
    {
      "platform": "linux",
      "product": "openssl",
      "release": "Debian 13.5 (trixie)",
      "fixedVersion": "3.5.7-1~deb13u2",
      "fix": "DEBIAN-CVE-2026-63073",
      "url": "https://patchblox.com/security/fix/linux/debian-cve-2026-63073",
      "released": "2026-08-26T00:17:14Z"
    },
    {
      "platform": "linux",
      "product": "openssl",
      "release": "Debian 14",
      "fixedVersion": "3.6.4-1",
      "fix": "DEBIAN-CVE-2026-63073",
      "url": "https://patchblox.com/security/fix/linux/debian-cve-2026-63073",
      "released": "2026-08-26T00:17:14Z"
    },
    {
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      "product": "openssl",
      "release": "RHEL 10",
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      "fix": "RHSA-2026:67154",
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      "released": "2026-09-14T12:58:54Z"
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      "fix": "RHSA-2026:67165",
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      "released": "2026-09-19T18:32:55Z"
    },
    {
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      "product": "openssl",
      "release": "Ubuntu 26.04.1 LTS (resolute)",
      "fixedVersion": "3.5.5-1ubuntu3.4",
      "fix": "openssl 3.5.5-1ubuntu3.4",
      "url": "https://patchblox.com/security/fix/linux/ubuntu-resolute-openssl-3.5.5-1ubuntu3.4",
      "released": "2026-08-24T17:00:00Z"
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      "fix": "RLSA-2026:67154",
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      "released": "2026-09-02T15:55:21Z"
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      "released": "2026-09-07T08:29:17Z"
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  ],
  "noFixYet": [],
  "dataAsOf": "2026-11-08T19:12:23Z",
  "attribution": {
    "text": "Data: Patchblox Patch Radar",
    "url": "https://patchblox.com/security/patch-radar",
    "terms": "https://patchblox.com/security/patch-radar/use-the-data"
  }
}