CVE-2026-75806

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.