Issue summary: An established DTLS 1.2 association using an AEAD cipher suite can be terminated by a single unauthenticated datagram whose encrypted fragment is shorter than the mandatory explicit IV and authentication tag overhead. Imp…

Overview

Issue summary: An established DTLS 1.2 association using an AEAD cipher suite can be terminated by a single unauthenticated datagram whose encrypted fragment is shorter than the mandatory explicit IV and authentication tag overhead.

Impact summary: An attacker who can send a datagram that is routed to an existing DTLS 1.2 association can tear that association down without knowing any key material. This is a Denial of Service limited to the targeted association. There is no memory safety or confidentiality impact.

CWE: CWE-1284: Improper Validation of Specified Quantity in Input

Description: In TLS 1.2 and DTLS 1.2 every record protected by an AEAD cipher suite carries an explicit IV followed by the ciphertext and an authentication tag. When decrypting such a record the record layer passed the record length to the cipher implementation before checking that the record was long enough to contain the explicit IV and the tag. For a record shorter than that overhead the cipher implementation rejected the impossible length, and the record layer treated this as an internal failure and raised a fatal internal_error alert instead of treating the record as one that failed authentication.

In TLS 1.2 the same record causes a fatal internal_error alert instead of the expected bad_record_mac alert. Since any undecryptable record already terminates a TLS connection, this is a protocol conformance issue rather than a security issue in TLS.

The fix validates the record length against the explicit IV and tag length before any AEAD processing, so that TLS reports bad_record_mac and DTLS silently discards the record.

FIPS impact: no The affected code is outside the FIPS module boundary.

Affected

• openssl >= 1.1.1, < 1.1.1zj
• openssl >= 3.0.0, < 3.0.23
• openssl >= 3.4.0, < 3.4.8
• openssl >= 3.5.0, < 3.5.9
• openssl >= 3.6.0, < 3.6.5
• openssl >= 4.0.0, < 4.0.3

Remediation

Upgrade past the affected range:

• openssl 4.0.3

Vendor advisories

• Red Hat VEX · Moderate · affected: Red Hat Developer Hub, Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 6, Red Hat Enterprise Linux 7, Red Hat Enterprise Linux 8, Red Hat Enterprise Linux 9, … · no fix planned: Red Hat Enterprise Linux 6, Red Hat Developer Hub, Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 7, … · updated 2026-09-29 · vex