Go standard library Crypto/tls vulnerabilities

CVE-2026-97031 High · 7.5 CWE-405 Oct 8, 2026

Reject malformed ECH outer extension references in crypto/tls

Multiple ECH outer extension references are not permitted under RFC 9849; previously, a client could send a well-crafted packet that could trigger memory exhaustion in the server process by specifying multiple references. We now reject these as malformed and curb the memory amplification vector as a result.

CVE-2026-56862 High · 7.5 CWE-770 Aug 13, 2026

Limit handshake messages we are willing to accept post-handshake in crypto/tls

Handshake messages, such as KeyUpdate, are always considered as state-advancing, regardless of whether a handshake has been completed or not. As a result, a malicious client can keep sending KeyUpdate messages to force the server to keep performing key derivation operations indefinitely.

CVE-2026-42505 Medium · 5.3 CWE-201 Jul 8, 2026

Invoking Encrypted Client Hello privacy leak in crypto/tls

Handshakes which used Encrypted Client Hello could be de-anonymized by a passive network observer due to a disclosure of pre-shared key identities in the unencrypted client hello.

CVE-2026-32283 High · 7.5 CWE-770 Apr 7, 2026

Unauthenticated TLS 1.3 KeyUpdate record can cause persistent connection retention and DoS in crypto/tls

If one side of the TLS connection sends multiple key update messages post-handshake in a single record, the connection can deadlock, causing uncontrolled consumption of resources. This can lead to a denial of service. This only affects TLS 1.3.

CVE-2025-68121 Critical · 10.0 CWE-295 Feb 5, 2026

Go crypto/tls session resumption certificate validation flaw

During session resumption in crypto/tls, if the underlying Config has its ClientCAs or RootCAs fields mutated between the initial handshake and the resumed handshake, the resumed handshake may succeed when it should have failed. This may happen when a user calls Config.Clone and mutates the returned Config, or uses Config.GetConfigForClient. This can cause a client to resume a session with a server that it would not have resumed with during the initial handshake, or cause a server to resume a session with a client that it would not have resumed with during the initial handshake.

CVE-2025-61730 Medium · 5.3 Jan 28, 2026

Handshake messages may be processed at the incorrect encryption level in crypto/tls

During the TLS 1.3 handshake if multiple messages are sent in records that span encryption level boundaries (for instance the Client Hello and Encrypted Extensions messages), the subsequent messages may be processed before the encryption level changes. This can cause some minor information disclosure if a network-local attacker can inject messages during the handshake.

CVE-2025-58189 Medium · 5.3 CWE-532 Oct 29, 2025

ALPN negotiation error contains attacker controlled information in crypto/tls

When Conn.Handshake fails during ALPN negotiation the error contains attacker controlled information (the ALPN protocols sent by the client) which is not escaped.