# CVE-2026-75806: Unauthenticated and Undersized DTLS 1.2 AEAD Record Causes DoS

Status: published. Published: 2026-09-29. Updated: 2026-11-10.

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.

## Remediation

- fix: The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches. (source: CNA: openssl) — https://github.com/openssl/openssl/commit/04728a289a823e68137f88da016cb9ede307217d
- fix: The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches. (source: CNA: openssl) — https://github.com/openssl/openssl/commit/050b275cd671a6eed1d6457642d41a5a77aab972
- fix: The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches. (source: CNA: openssl) — https://github.com/openssl/openssl/commit/3a4589d015a9049d47b66f186cf50a8711343a1d
- fix: The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches. (source: CNA: openssl) — https://github.com/openssl/openssl/commit/5af82fefbaf2b5fec2fc0e1d87f112844902f01d

## Affected products and versions

- OpenSSL / OpenSSL: ≥ 4.0.0; < 4.0.3 (affected, semver); ≥ 3.6.0; < 3.6.5 (affected, semver); ≥ 3.5.0; < 3.5.9 (affected, semver); ≥ 3.4.0; < 3.4.8 (affected, semver); ≥ 3.0.0; < 3.0.23 (affected, semver); ≥ 1.1.1; < 1.1.1zj (affected, custom). Source: CNA: openssl
- Siemens / SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AB0): ≥ V3.1.7; < * (affected, custom). Source: ADP: siemens-SADP
- Siemens / SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AC0): ≥ V3.1.7; < * (affected, custom). Source: ADP: siemens-SADP
- Siemens / SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AB0): ≥ V3.1.7; < * (affected, custom). Source: ADP: siemens-SADP
- Siemens / SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AC0): ≥ V3.1.7; < * (affected, custom). Source: ADP: siemens-SADP
- Siemens / SIPLUS S7-1500 CPU 1518-4 PN/DP MFP (6AG1518-4AX00-4AC0): ≥ V3.1.7; < * (affected, custom). Source: ADP: siemens-SADP

## Severity and prioritization

- CVSS 3.1: 5.3 (medium); CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L; source: ADP: CISA-ADP

- CISA KEV: No listing in collected sources

- EPSS: 1.10% as of 2026-11-09; percentile 66.01%

- SSVC: exploitation none; automatable yes; technical impact partial; source ADP: CISA-ADP

- Weaknesses: CWE-1284

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://openssl-library.org/news/secadv/20260929.txt (CNA: openssl; vendor-advisory)

- https://github.com/openssl/openssl/commit/04728a289a823e68137f88da016cb9ede307217d (CNA: openssl; patch)

- https://github.com/openssl/openssl/commit/050b275cd671a6eed1d6457642d41a5a77aab972 (CNA: openssl; patch)

- https://github.com/openssl/openssl/commit/3a4589d015a9049d47b66f186cf50a8711343a1d (CNA: openssl; patch)

- https://github.com/openssl/openssl/commit/5af82fefbaf2b5fec2fc0e1d87f112844902f01d (CNA: openssl; patch)

- https://cert-portal.siemens.com/productcert/html/ssa-457936.html (ADP: siemens-SADP)

## Provenance

- CNA: openssl: https://www.cve.org/CVERecord?id=CVE-2026-75806; retrieved 2026-11-10; source updated 2026-11-10

- FIRST EPSS: https://api.first.org/data/v1/epss?cve=CVE-2026-75806; retrieved 2026-11-10; source updated Not reported

Revision: ba4303537e0caa5913497d5d385cee28b773ec01cb484fe43301af8d652acbfe

Canonical: https://y2.dev/cve/CVE-2026-75806

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