Incorrect Tag Processing for Empty Messages in AES-GCM-SIV and AES-SIV modes

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Summary

CVECVE-2026-45446
StatePUBLISHED
Assigneropenssl
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-06-09 17:17:19 UTC
Updated2026-06-10 08:16:24 UTC
DescriptionIssue summary: The implementations of AES-SIV (RFC 5297) and AES-GCM-SIV (RFC 8452) mishandle the authentication of AAD (Additional Authenticated Data) with an empty ciphertext allowing a forgery of such messages. Impact summary: An attacker can forge empty messages with arbitrary AAD to the victim's application using these ciphers. AES-SIV (RFC 5297) and AES-GCM-SIV (RFC 8452) are nonce-misuse-resistant AEAD modes: they accept a key, nonce, optional AAD (bytes that are authenticated but not encrypted), and plaintext, and produces ciphertext plus a 16-byte tag. On decrypt, `EVP_DecryptFinal_ex()` is documented to return success only if the tag is verified succesfully. In OpenSSL's provider implementation of these ciphers, the expected tag is computed only when decryption function is invoked with non-empty data. If the caller supplies AAD and then calls `EVP_DecryptFinal_ex()` without invocation of the ciphertext update, which can happen when the received ciphertext length is zero, the tag is never recalculated and still holds its all-zeros value. When AES-GCM-SIV is used, an attacker who sends arbitrary AAD, empty ciphertext, and all-zeros tag passes authentication under any key they do not know, single-shot. When AES-SIV is used, for mounting the attack it's necessary for the application to reuse the decryption context without resetting the key. AES-SIV is implemented since OpenSSL 3.0. AES-GCM-SIV is implemented since OpenSSL 3.2. No protocols implemented in OpenSSL itself (TLS/CMS/PKCS7/HPKE/QUIC) support either AES-GCM-SIV or AES-SIV. To mount an attack, the applications must implement their own protocol and use the EVP interface. Also they must skip the ciphertext update when a message with an empty ciphertext arrives. The FIPS modules in 4.0, 3.6, 3.5, 3.4, and 3.0 are not affected by this issue, as these algorithms are not FIPS approved and the affected code is outside the OpenSSL FIPS module boundary.

Risk And Classification

Primary CVSS: v3.1 4.8 MEDIUM from ADP

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N

Problem Types: CWE-325 | CWE-325 CWE-325 Missing Cryptographic Step

VersionSourceTypeScoreSeverityVector
3.1ADPDECLARED4.8MEDIUMCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N
3.1134c704f-9b21-4f2e-91b3-4a467353bcc0Secondary4.8MEDIUMCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
High
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
Low
Integrity
Low
Availability
None

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA OpenSSL OpenSSL affected 4.0.0 4.0.1 semver Not specified
CNA OpenSSL OpenSSL affected 3.6.0 3.6.3 semver Not specified
CNA OpenSSL OpenSSL affected 3.5.0 3.5.7 semver Not specified
CNA OpenSSL OpenSSL affected 3.4.0 3.4.6 semver Not specified
CNA OpenSSL OpenSSL affected 3.0.0 3.0.21 semver Not specified

References

ReferenceSourceLinkTags
github.com/openssl/openssl/commit/7fe3f33a3b3a4c487aa4dcdbc87057f66ffd2b85 [email protected] github.com
github.com/openssl/openssl/commit/eec5e9bf0d867333b8495e456f5235d225798a68 [email protected] github.com
github.com/openssl/openssl/commit/25b32cd9d41d2bc01b6abc425bb4baf2c2236fdc [email protected] github.com
openssl-library.org/news/secadv/20260609.txt [email protected] openssl-library.org
github.com/openssl/openssl/commit/71e2a5d263518cf5866043bd60ee4994d59e53a3 [email protected] github.com
github.com/openssl/openssl/commit/daca0f48e4a69a2892a62262bad59e62a8a76598 [email protected] github.com
github.com/openssl/security/commit/25b32cd9d41d2bc01b6abc425bb4baf2c2236fdc MITRE github.com
github.com/openssl/security/commit/71e2a5d263518cf5866043bd60ee4994d59e53a3 MITRE github.com
github.com/openssl/security/commit/7fe3f33a3b3a4c487aa4dcdbc87057f66ffd2b85 MITRE github.com
github.com/openssl/security/commit/daca0f48e4a69a2892a62262bad59e62a8a76598 MITRE github.com
github.com/openssl/security/commit/eec5e9bf0d867333b8495e456f5235d225798a68 MITRE github.com
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis

Vendor Comments And Credit

Discovery Credit

CNA: Alex Gaynor (Anthropic) (en)

CNA: Dmitry Belyavskiy (Red Hat) (en)

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