CVE-2026-75806

About vulnerability

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 product:

AlmaLinux 9.2 ESU , Alpine Linux 3.23 , Alpine Linux 3.24 , CentOS 7 ELS , CentOS 8.4 ELS , CentOS 8.5 ELS , CentOS Stream 8 ELS , CloudLinux 7 ELS , Debian 10 , Debian 10 ELS , Debian 11 , Debian 11 ELS , Debian 12 , Debian 13 , EL 10 , EL 7 , EL 8 , EL 9 , Oracle Linux 7 ELS , RHEL 7 ELS , TuxCare 9.6 ESU , TuxCare 9.8 ESU , Ubuntu 16.04 , Ubuntu 18.04 , Ubuntu 18.04 ELS , Ubuntu 20.04 , Ubuntu 20.04 ELS , Ubuntu 22.04 , Ubuntu 24.04 , Ubuntu 26.04

Affected packages:

openssl11 @ 1.1.1k (+34 more)