CVE-2026-45445

AES-OCB IV Ignored on EVP_Cipher() Path

Published Jun 9, 2026 CVSS 3.1 · 7.5 High EPSS < 1% KEV · Not listed
Description
Issue summary: When an application drives an AES-OCB context through the
public EVP_Cipher() one-shot interface, the application-supplied
initialisation vector (IV) is silently discarded.

Impact summary: Every message encrypted under the same key uses the
same effective nonce regardless of the IV supplied by the caller,
resulting in (key, nonce) reuse and loss of confidentiality. If the
same code path is used to compute the authentication tag, the tag
depends only on the (key, IV) pair and not on the plaintext or
ciphertext, allowing universal forgery of arbitrary ciphertext from a
single captured message.

OpenSSL provides two ways to drive a cipher: the documented streaming
interface (EVP_CipherUpdate / EVP_CipherFinal_ex) and a lower-level
one-shot, EVP_Cipher(), whose documentation explicitly recommends
against use by applications in favour of EVP_CipherUpdate() and
EVP_CipherFinal_ex(). The OCB provider's streaming handler flushes
the application-supplied IV into the OCB context before processing
data; the one-shot handler did not. Every call to EVP_Cipher() on an
AES-OCB context therefore ran with the all-zero key-derived offset
state left by cipher initialisation, regardless of the caller's IV.

If EVP_EncryptFinal_ex() is subsequently used to obtain the
authentication tag, the deferred IV setup runs at that point and
clears the running checksum that should have been accumulated over the
plaintext. The resulting tag is a function of (key, IV) only and
verifies against any ciphertext produced under the same (key, IV)
pair.

The OpenSSL SSL/TLS implementation is not affected: AES-OCB is not a
TLS cipher suite, and libssl does not call EVP_Cipher() in any case.
Applications that drive AES-OCB through the documented streaming AEAD
API (EVP_CipherUpdate / EVP_CipherFinal_ex) are not affected. Only
applications that combine the AES-OCB cipher with the EVP_Cipher()
one-shot API are vulnerable.

The FIPS modules in 4.0, 3.6, 3.5, 3.4 and 3.0 are not affected by
this issue, as AES-OCB is outside the OpenSSL FIPS module boundary.

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

Source ID Title
Debian DSA Debian DSA DSA-6335-1 openssl security update
Ubuntu USN Ubuntu USN USN-8414-1 OpenSSL vulnerabilities
History
Type Values Removed Values Added
CPEs cpe:2.3:a:openssl:openssl:*:*:*:*:*:*:*:*
cpe:2.3:a:openssl:openssl:4.0.0:-:*:*:*:*:*:*
Type Values Removed Values Added
Metrics cvssV3_1

{'score': 7.5, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N'}

ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Type Values Removed Values Added
First Time appeared Openssl
Openssl openssl
Vendors & Products Openssl
Openssl openssl
Type Values Removed Values Added
Description Issue summary: When an application drives an AES-OCB context through the public EVP_Cipher() one-shot interface, the application-supplied initialisation vector (IV) is silently discarded. Impact summary: Every message encrypted under the same key uses the same effective nonce regardless of the IV supplied by the caller, resulting in (key, nonce) reuse and loss of confidentiality. If the same code path is used to compute the authentication tag, the tag depends only on the (key, IV) pair and not on the plaintext or ciphertext, allowing universal forgery of arbitrary ciphertext from a single captured message. OpenSSL provides two ways to drive a cipher: the documented streaming interface (EVP_CipherUpdate / EVP_CipherFinal_ex) and a lower-level one-shot, EVP_Cipher(), whose documentation explicitly recommends against use by applications in favour of EVP_CipherUpdate() and EVP_CipherFinal_ex(). The OCB provider's streaming handler flushes the application-supplied IV into the OCB context before processing data; the one-shot handler did not. Every call to EVP_Cipher() on an AES-OCB context therefore ran with the all-zero key-derived offset state left by cipher initialisation, regardless of the caller's IV. If EVP_EncryptFinal_ex() is subsequently used to obtain the authentication tag, the deferred IV setup runs at that point and clears the running checksum that should have been accumulated over the plaintext. The resulting tag is a function of (key, IV) only and verifies against any ciphertext produced under the same (key, IV) pair. The OpenSSL SSL/TLS implementation is not affected: AES-OCB is not a TLS cipher suite, and libssl does not call EVP_Cipher() in any case. Applications that drive AES-OCB through the documented streaming AEAD API (EVP_CipherUpdate / EVP_CipherFinal_ex) are not affected. Only applications that combine the AES-OCB cipher with the EVP_Cipher() one-shot API are vulnerable. The FIPS modules in 4.0, 3.6, 3.5, 3.4 and 3.0 are not affected by this issue, as AES-OCB is outside the OpenSSL FIPS module boundary.
Title AES-OCB IV Ignored on EVP_Cipher() Path
Weaknesses CWE-325
References
Weaknesses

Sources

Status
PUBLISHED
Assigner
openssl
Published
Updated
Jun 10, 2026, 7:48 AM
Reserved
May 12, 2026, 2:34 PM
Status
Analyzed
Published
Jun 9, 2026, 5:17 PM
Modified
Jul 23, 2026, 8:10 AM
Severity
Moderate
Public date
Jun 9, 2026, 12:00 AM