CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:HIssue 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. A flaw was found in OpenSSL. A malicious CMP (Certificate Management Protocol) endpoint can send an unexpected distinguished name (DN) directly as the format string argument to ERR_raise_data(), causing the application to dereference and write to unrelated stack contents. This can lead to a crash in the CMP client, resulting in a denial of service.
Multiple vulnerabilities have been discovered in OpenSSL, allowing for denial of service attacks and policy bypasses. These vulnerabilities affect various OpenSSL versions and could be exploited by attackers. Users are a…