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CVE-2026-63073 — Untrusted Sender DN Used as Format String in CMP Response Validation

Affected: OpenSSL

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 imple…

USN-8678-1 — openssl vulnerabilities

Affected: Ubuntu:22.04:LTS: openssl, Ubuntu:24.04:LTS: openssl, Ubuntu:26.04:LTS: openssl

It was discovered that OpenSSL incorrectly handled the QUIC server incoming channel queue. A remote attacker could possibly use this issue to cause OpenSSL to use excessive resources, leading to a denial of service. This issue only affected Ubuntu 26.04 LTS. (CVE-2026-14456)

It was discovered that OpenSSL incorrectly handled signature algorithm selection when using Raw Public Keys. A remote attacker could possibly use this issue to cause OpenSSL to crash, resulting in a denial of service. This issue only affected Ubuntu 26.04 LTS. (CVE-2026-14457)

It was discovered that OpenSSL incorrectly handled QUIC INITIAL packet processing. A remote attacker could possibly use this issue to cause OpenSSL to crash, resulting in a denial of service. This issue only affected Ubuntu 26.04 LTS. (CVE-2026-18798)

It was discovered that OpenSSL incorrectly handled buffering of DTLS records for a future epoch. A remote attacker could possibly use this issue to cause OpenSSL to use excessive resources, leading to a denial of service. (CVE-2026-54874)

It was discovered that OpenSSL incorrectly handled CMS key unwrapping. A remote attacker could possibly use this issue to cause a heap buffer overflow, leading to a denial of service or arbitrary code execution. (CVE-2026-63072)

It was discovered that OpenSSL incorrectly validated the sender distinguished name in CMP response messages. A remote attacker could possibly use this issue to cause OpenSSL to crash, resulting in a denial of service. Th…