OpenSSL up to 4.0.1 AEAD Tag Verification EVP_Cipher integrity check

Summaryinfo

A vulnerability described as critical has been identified in OpenSSL up to 3.0.21/3.4.6/3.5.7/3.6.3/4.0.1. The impacted element is the function EVP_Cipher of the component AEAD Tag Verification. Executing a manipulation can lead to integrity check. This vulnerability is registered as CVE-2026-75803. It is possible to launch the attack remotely. No exploit is available.

Detailsinfo

A vulnerability has been found in OpenSSL up to 3.0.21/3.4.6/3.5.7/3.6.3/4.0.1 and classified as critical. This vulnerability affects the function EVP_Cipher of the component AEAD Tag Verification. The manipulation with an unknown input leads to a integrity check vulnerability. The CWE definition for the vulnerability is CWE-354. The product does not validate or incorrectly validates the integrity check values or "checksums" of a message. This may prevent it from detecting if the data has been modified or corrupted in transmission. As an impact it is known to affect confidentiality, integrity, and availability. CVE summarizes:

Issue summary: ChaCha20-Poly1305 and AES-OCB decryption with an empty ciphertext can report success without verifying the supplied authentication tag when the operation is finalized by calling the EVP_Cipher() function. Impact summary: Applications calling EVP_Cipher() on an empty ciphertext and expecting the call to check the AEAD tag may accept forged messages. CWE: CWE-354 (Improper Validation of Integrity Check Value) Description: The EVP_Cipher() API call for AEAD ciphers behaves like a one shot encryption and decryption call. It also verifies the AEAD tag after the decryption operation. However for AES-OCB and ChaCha20-Poly1305 ciphers it skipped the AEAD tag verification when an empty ciphertext was passed to the function. The callers of this function might believe that a successful return indicates a valid AEAD tag for these ciphers, even when that has not truly been validated in this case. FIPS impact: no The FIPS modules in 4.0, 3.6, 3.5, 3.4, and 3.0 are not affected by this CVE as the affected algorithms are not FIPS approved and thus not implemented in the FIPS module.

The advisory is available at openssl-library.org. This vulnerability was named CVE-2026-75803 since 08/18/2026. The exploitation appears to be easy. The attack can be initiated remotely. No form of authentication is required for a successful exploitation. Technical details are known, but there is no available exploit. The structure of the vulnerability defines a possible price range of USD $5k-$25k at the moment (estimation calculated on 08/25/2026).

Upgrading to version 3.0.22, 3.4.7, 3.5.8, 3.6.4 or 4.0.2 eliminates this vulnerability.

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Productinfo

Type

• Network Encryption Software

Name

• OpenSSL

Version

• 3.0.0
• 3.0.1
• 3.0.2
• 3.0.3
• 3.0.4
• 3.0.5
• 3.0.6
• 3.0.7
• 3.0.8
• 3.0.9
• 3.0.10
• 3.0.11
• 3.0.12
• 3.0.13
• 3.0.14
• 3.0.15
• 3.0.16
• 3.0.17
• 3.0.18
• 3.0.19
• 3.0.20
• 3.0.21
• 3.4.0
• 3.4.1
• 3.4.2
• 3.4.3
• 3.4.4
• 3.4.5
• 3.4.6
• 3.5.0
• 3.5.1
• 3.5.2
• 3.5.3
• 3.5.4
• 3.5.5
• 3.5.6
• 3.5.7
• 3.6.0
• 3.6.1
• 3.6.2
• 3.6.3
• 4.0.0
• 4.0.1

License

• open-source

Website

• Product: https://www.openssl.org/

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