CVE-2025-66199 — TLS 1.3 CompressedCertificate excessive memory allocation

Affected: OpenSSL

Issue summary: A TLS 1.3 connection using certificate compression can be forced to allocate a large buffer before decompression without checking against the configured certificate size limit.

Impact summary: An attacker can cause per-connection memory allocations of up to approximately 22 MiB and extra CPU work, potentially leading to service degradation or resource exhaustion (Denial of Service).

In affected configurations, the peer-supplied uncompressed certificate length from a CompressedCertificate message is used to grow a heap buffer prior to decompression. This length is not bounded by the max_cert_list setting, which otherwise constrains certificate message sizes. An attacker can exploit this to cause large per-connection allocations followed by handshake failure. No memory corruption or information disclosure occurs.

This issue only affects builds where TLS 1.3 certificate compression is compiled in (i.e., not OPENSSL_NO_COMP_ALG) and at least one compression algorithm (brotli, zlib, or zstd) is available, and where the compression extension is negotiated. Both clients receiving a server CompressedCertificate and servers in mutual TLS scenarios receiving a client CompressedCertificate are affected. Servers that do not request client certificates are not vulnerable to client-initiated attacks.

Users can mitigate this issue by setting SSL_OP_NO_RX_CERTIFICATE_COMPRESSION to disable receiving compressed certificates.

The FIPS modules in 3.6, 3.5, 3.4 and 3.3 are n…

USN-7980-1 — openssl vulnerabilities

Affected: Ubuntu:22.04:LTS: openssl, Ubuntu:24.04:LTS: openssl, Ubuntu:25.10: openssl

Stanislav Fort, Petr Šimeček, and Hamza discovered that OpenSSL incorrectly validated PBMAC1 parameters when doing PKCS#12 MAC verification. An attacker could possibly use this issue to cause OpenSSL to crash, resulting in a denial of service. This issue only affected Ubuntu 25.10. (CVE-2025-11187)

Stanislav Fort discovered that OpenSSL incorrectly parsed CMS AuthEnvelopedData messages. An attacker could possibly use this issue to cause OpenSSL to crash, resulting in a denial of service. (CVE-2025-15467)

Stanislav Fort discovered that OpenSSL incorrectly handled memory in the SSL_CIPHER_find() function. An attacker could possibly use this issue to cause OpenSSL to crash, resulting in a denial of service. This issue only affected Ubuntu 25.10. (CVE-2025-15468)

Stanislav Fort discovered that the OpenSSL "openssl dgst" command line tool incorrectly truncated data to 16MB. An attacker could posibly use this issue to hide unauthenticated data beyond the 16MB limit. This issue only affected Ubuntu 25.10. (CVE-2025-15469)

Tomas Dulka and Stanislav Fort discovered that OpenSSL incorrectly handled memory with TLS 1.3 connections using certificate compression. An attacker could possibly use this issue to consume resources, leading to a denial of service. This issue only affected Ubuntu 25.10. (CVE-2025-66199)

Petr Simecek and Stanislav Fort discovered that OpenSSL incorrectly handled memory when writing large data into a BIO chain. An attacker could possibly use this issue to con…

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CVE-2025-66199 — TLS 1.3 CompressedCertificate excessive memory allocation

USN-7980-1 — openssl vulnerabilities