--- id: CVE-2026-63073 title: |- Issue summary: OpenSSL CMP response validation passed an unexpected response sender distinguished name directly as the format string to `ERR_raise_data()`. Impact summary: A malicious or intercepted CMP endpoint can crash a CMP client t… summary: |- Issue summary: OpenSSL CMP response validation passed an unexpected response sender distinguished name directly as the format string to `ERR_raise_data()`. Impact summary: A malicious or intercepted CMP endpoint can crash a CMP client t… severity: critical cvss: 9.8 cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H' cwe: - CWE-134 vendor: openssl product: openssl affected: - 'openssl >= 3.4.0, < 3.4.7' - 'openssl >= 3.5.0, < 3.5.8' - 'openssl >= 3.6.0, < 3.6.4' - 'openssl >= 4.0.0, < 4.0.2' patched: - openssl 4.0.2 published: '2026-08-25' updated: '2026-09-11' sourceUpdated: '2026-09-11T21:16:45.633' source: NVD sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-63073' references: - url: >- https://github.com/openssl/openssl/commit/0cc20b322639919aa423e90799d9a57c3b4b76ca label: openssl-security@openssl.org - url: >- https://github.com/openssl/openssl/commit/6a0acc072b4d37a7cac1252a29c1ce1f00c5ec29 label: openssl-security@openssl.org - url: >- https://github.com/openssl/openssl/commit/7eb2e3ec9d1d4f35c8022fccd4b03398b3f33e21 label: openssl-security@openssl.org - url: >- https://github.com/openssl/openssl/commit/a7e5a6eea8fd3ccca6b6fbba031a5fbf8a3d93b4 label: openssl-security@openssl.org - url: 'https://openssl-library.org/news/secadv/20260825.txt' label: openssl-security@openssl.org - url: >- https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-63073.json - url: 'https://access.redhat.com/security/cve/CVE-2026-63073' - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2517565' - url: 'https://www.cve.org/CVERecord?id=CVE-2026-63073' - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-63073' - url: 'https://access.redhat.com/errata/RHSA-2026:67154' - url: 'https://access.redhat.com/errata/RHSA-2026:67165' - url: 'https://access.redhat.com/errata/RHSA-2026:59641' - url: 'https://access.redhat.com/errata/RHSA-2026:59635' - url: 'https://access.redhat.com/errata/RHSA-2026:67956' - url: 'https://access.redhat.com/errata/RHSA-2026:71603' tags: - nvd - csaf - vex - red-hat - score-dispute epss: 0.01159 epssPercentile: 0.65745 ingestedAt: '2026-09-12T00:03:49.031Z' scores: nvd: 9.8 vendor: 5.9 --- ## Overview Issue summary: OpenSSL CMP response validation passed an unexpected response sender distinguished name directly as the format string to `ERR_raise_data()`. 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 "CN=%s%n" 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. ## Affected - `openssl >= 3.4.0, < 3.4.7` - `openssl >= 3.5.0, < 3.5.8` - `openssl >= 3.6.0, < 3.6.4` - `openssl >= 4.0.0, < 4.0.2` ## Remediation Upgrade past the affected range: - `openssl 4.0.2` ## Vendor advisories - **RHSA-2026:67154** · Red Hat · fixed in: Red Hat Enterprise Linux AppStream (v. 10), Red Hat Enterprise Linux BaseOS (v. 10) · released 2026-09-14 · [advisory](https://access.redhat.com/errata/RHSA-2026:67154) - **RHSA-2026:67165** · Red Hat · fixed in: Red Hat Enterprise Linux AppStream (v. 9), Red Hat Enterprise Linux BaseOS (v. 9) · released 2026-09-14 · [advisory](https://access.redhat.com/errata/RHSA-2026:67165) - **RHSA-2026:59641** · Red Hat · fixed in: Red Hat Hardened Images · released 2026-08-25 · [advisory](https://access.redhat.com/errata/RHSA-2026:59641) - **RHSA-2026:59635** · Red Hat · fixed in: Red Hat Hardened Images · released 2026-08-25 · [advisory](https://access.redhat.com/errata/RHSA-2026:59635) - **Red Hat VEX** · Low · affected: Red Hat Developer Hub, Red Hat Enterprise Linux 10, Red Hat JBoss Core Services, Red Hat JBoss Web Server 6, Red Hat JBoss Web Server 7, Red Hat OpenShift Container Platform 4 · no fix planned: Red Hat Developer Hub, Red Hat Enterprise Linux 10, Red Hat JBoss Core Services, Red Hat JBoss Web Server 6, … · updated 2026-09-24 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-63073.json) - **RHSA-2026:67956** · Red Hat · fixed in: Red Hat Update Infrastructure 5 · released 2026-09-16 · [advisory](https://access.redhat.com/errata/RHSA-2026:67956) - **RHSA-2026:71603** · Red Hat · fixed in: Red Hat Update Infrastructure 5 · released 2026-09-24 · [advisory](https://access.redhat.com/errata/RHSA-2026:71603)