Update to OpenSSL 3.5.6, a security patch release. The most severe CVE fixed is Medium.

Bug fixes:

• Incorrect failure handling in RSA KEM RSASVE encapsulation (CVE-2026-31790).
• Loss of key agreement group tuple structure when the DEFAULT keyword is used in the server-side configuration of the key-agreement group list (CVE-2026-2673).
• Potential use-after-free in DANE client code (CVE-2026-28387).
• NULL pointer dereference when processing a delta CRL (CVE-2026-28388).
• Possible NULL dereference when processing CMS KeyAgreeRecipientInfo (CVE-2026-28389).
• Possible NULL dereference when processing CMS KeyTransportRecipientInfo (CVE-2026-28390).
• Heap buffer overflow in hexadecimal conversion (CVE-2026-31789).
• Broken detection of plantext HTTP over TLS.

Update to OpenSSL 3.5.5, a security patch release. The most severe CVE fixed is High.

Bug fixes:

• Improper validation of PBMAC1 parameters in PKCS#12 MAC verification (CVE-2025-11187).
• Stack buffer overflow in CMS AuthEnvelopedData parsing (CVE-2025-15467).
• NULL dereference in SSL_CIPHER_find function on unknown cipher ID (CVE-2025-15468).
• TLS 1.3 CompressedCertificate excessive memory allocation (CVE-2025-66199).
• Heap out-of-bounds write in BIO_f_linebuffer on short writes (CVE-2025-68160).
• Unauthenticated/unencrypted trailing bytes with low-level OCB function calls (CVE-2025-69418).
• Out of bounds write in PKCS12_get_friendlyname UTF-8 conversion (CVE-2025-69419).
• Missing ASN1_TYPE validation in TS_RESP_verify_response() function (CVE-2025-69420).
• NULL Pointer Dereference in PKCS12_item_decrypt_d2i_ex function (CVE-2025-69421).
• Missing ASN1_TYPE validation in PKCS#12 parsing (CVE-2026-22795).
• ASN1_TYPE Type Confusion in the PKCS7_digest_from_attributes function (CVE-2026-22796).

Update to OpenSSL 3.5.4, a moderate severity security release.

• Fix Out-of-bounds read & write in RFC 3211 KEK Unwrap (CVE-2025-9230).
• Fix Out-of-bounds read in HTTP client no_proxy handling (CVE-2025-9232).
• Fixed the length of the ASN.1 sequence for the SM3 digests of RSA-encrypted signatures.

Update to OpenSSL 3.5.3.

• Support Delphi 13 Florence Win32 and Win64.

First release, based on OpenSSL 3.5.2.

Changes from OpenSSL 3.4:

Potentially significant or incompatible changes:

• Default encryption cipher for the req, cms, and smime applications changed from des-ede3-cbc to aes-256-cbc.
• The default TLS supported groups list has been changed to include and prefer hybrid PQC KEM groups. Some practically unused groups were removed from the default list.
• The default TLS keyshares have been changed to offer X25519MLKEM768 and X25519.
• All BIO_meth_get_*() functions were deprecated.

New features:

• Support for server side QUIC (RFC 9000).
• Support for 3rd party QUIC stacks including 0-RTT support.
• Support for PQC algorithms (ML-KEM, ML-DSA and SLH-DSA).
• Support added for opaque symmetric key objects (EVP_SKEY).
• Support for multiple TLS keyshares and improved TLS key establishment group configurability.
• API support for pipelining in provided cipher algorithms.