CVE-2026-75803
Received Received - Intake

BaseFortify

Publication date: 2026-08-25

Last updated on: 2026-08-25

Assigner: OpenSSL Software Foundation

Description
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.

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Meta Information

Published
2026-08-25
Last Modified
2026-08-25
Generated
2026-08-25
AI Q&A
2026-08-25
EPSS Evaluated
N/A
NVD
CVE-2026-75803
EUVD
EUVD-2026-65488

Affected Vendors & Products

Showing 1 associated CPE
Vendor Product Version / Range
openssl openssl *

Helpful Resources

Exploitability

CWE
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KEV
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CWE ID Description
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.

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Executive Summary

This vulnerability affects ChaCha20-Poly1305 and AES-OCB ciphers in OpenSSL. When decrypting an empty ciphertext using EVP_Cipher(), the function may incorrectly report success without verifying the authentication tag. This allows forged messages to be accepted as valid.

Detection Guidance

This vulnerability affects OpenSSL's AEAD cipher implementations. To detect it, check your OpenSSL version and verify if it includes the fix. Use commands like 'openssl version' to check the version and compare it against patched releases. Inspect applications using OpenSSL for calls to EVP_Cipher() with NULL inputs during finalization.

Impact Analysis

Applications using EVP_Cipher() for decryption with these ciphers could process invalid or malicious data without detecting tampering. This may lead to unauthorized access, data corruption, or other security breaches depending on the application's use case.

Compliance Impact

This vulnerability could potentially impact compliance with GDPR and HIPAA by allowing forged messages to be accepted as valid due to improper authentication tag validation. GDPR requires data integrity and security measures, while HIPAA mandates protection against unauthorized data alteration. The flaw in AEAD ciphers may undermine these requirements by failing to verify integrity check values during decryption.

Mitigation Strategies

Update OpenSSL to a patched version where EVP_Cipher() properly validates AEAD tags even for empty ciphertexts. Avoid using EVP_Cipher() with AES-OCB or ChaCha20-Poly1305 ciphers until patched.

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