CVE-2026-75803 AEAD Forgeries with Empty Ciphertext When Using EVP_Cipher()
Attackers can forge messages using ChaCha20-Poly1305 or AES-OCB with empty ciphertexts, bypassing authentication tag verification in OpenSSL.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-75803?
CVE-2026-75803 is a critical vulnerability in Openssl Openssl, published on 25 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official 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.
Weakness: CWE-354
Which versions are affected by CVE-2026-75803?
It affects 1 product.
Linux distribution packages (8)
bootupd Red Hat:hummingbird:1 | All versions | 0:0.2.36-3.hum1 |
ruby3.4 Red Hat:hummingbird:1 | All versions | 0:3.4.10-31.7.hum1 |
ruby3.4-bundled-gems Red Hat:hummingbird:1 | All versions | 0:3.4.10-31.7.hum1 |
ruby3.4-default-gems Red Hat:hummingbird:1 | All versions | 0:3.4.10-31.7.hum1 |
ruby3.4-devel Red Hat:hummingbird:1 | All versions | 0:3.4.10-31.7.hum1 |
ruby3.4-doc Red Hat:hummingbird:1 | All versions | 0:3.4.10-31.7.hum1 |
ruby3.4-libs Red Hat:hummingbird:1 | All versions | 0:3.4.10-31.7.hum1 |
rust-bootupd Red Hat:hummingbird:1 | All versions | 0:0.2.36-3.hum1 |
Products include Openssl Openssl.
How do I fix CVE-2026-75803?
Apply the vendor's patch.
Is CVE-2026-75803 being exploited?
There is no known exploitation of CVE-2026-75803 in the wild and no public exploit code.
Other vulnerabilities in Openssl Openssl
Sources
Also known as ALPINE-CVE-2026-75803, AZL-97671, AZL-97884, AZL-97935, BELL-CVE-2026-75803, CLEANSTART-2026-JP03196 and 10 more.