OpenSSL

CVE-2026-45446: Incorrect Tag Processing for Empty Messages in AES-GCM-SIV and AES-SIV modes

Is it exploited?

Not on CISA's list. CISA has not added it to the Known Exploited Vulnerabilities catalog as of 29 Oct 2026. If CISA adds it, this page shows it as known exploited.

How likely is exploitation in the next 30 days?

0.4%

Up from 0.2% on 22 Oct 2026.

EPSS score, percentile 38.1 of all scored records. A probability estimated by FIRST, not a report of exploitation.

How severe?

4.8 Medium

CVSS v3.1 base score, from CISA's enrichment of the record

What should I do?

CISA has set no required action, because the vulnerability is not in KEV.

Advisories and patches (6)

Which versions are affected?

Affected

from 4.0.0 to before 4.0.1
from 3.6.0 to before 3.6.3
from 3.5.0 to before 3.5.7
from 3.4.0 to before 3.4.6
from 3.0.0 to before 3.0.21

Versions by product

Source: CISA KEV 2026.10.29, as of 29 Oct 2026; FIRST EPSS, as of 29 Oct 2026; CVE List, as of 29 Oct 2026. About the data.

What to do

Advisories and patches

This summary is based on the CVE record as of 29 Oct 2026. Check the vendor's advisory before you act: affected versions and fixes can change.

Affected products and versions

As listed in the CVE record.

OpenSSL OpenSSL
Status	Versions
Affected	from 4.0.0 to before 4.0.1
Affected	from 3.6.0 to before 3.6.3
Affected	from 3.5.0 to before 3.5.7
Affected	from 3.4.0 to before 3.4.6
Affected	from 3.0.0 to before 3.0.21

Versions not listed are: unaffected.

Source: CVE List, as of 29 Oct 2026. About the data.

About this vulnerability

Summary: CVE record, as of 29 Oct 2026.

CISA has not added CVE-2026-45446 to its Known Exploited Vulnerabilities (KEV) catalog, as of 29 Oct 2026.
The CVE record was published on 9 Jun 2026.
The CVE record carries a CVSS v3.1 base score of 4.8 (Medium), taken from CISA's enrichment of the record.
FIRST's EPSS model puts the probability of exploitation in the next 30 days at 0.4% (percentile 38.1), as of 29 Oct 2026. EPSS is a statistical estimate, not a report of exploitation.
CISA's SSVC assessment in the CVE record: exploitation none, automatable no, technical impact partial.
The credits in the CVE record name Anthropic (Claude) as finder.

Source: CISA KEV 2026.10.29, as of 29 Oct 2026; CVE List, as of 29 Oct 2026; FIRST EPSS, as of 29 Oct 2026. About the data.

Description

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

Issue 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.

Source: CVE List, as of 29 Oct 2026. About the data.

Weakness

CWE-325

CWE-325: Missing Cryptographic Step

CWE and CAPEC are maintained by MITRE; the entries are those named in the CVE record.

Timeline

Date	Event
9 Jun 2026	CVE record published
10 Jun 2026	CVE record last updated

Known exploited OpenSSL vulnerabilities

CVE-2014-0160: OpenSSL Information Disclosure Vulnerability (added 4 May 2022)