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Vulnerability · Published Aug 25, 2026 · Assigned by openssl

CVE-2026-75803AEAD Forgeries with Empty Ciphertext When Using EVP_Cipher()

Critical 9.1

In plain English

A critical-severity security flaw in OpenSSL from OpenSSL. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 17% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)9.1Critical
Exploit odds (30 days)0.3%top 83.0% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known

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.

Affected packages & fixed versions

EcosystemPackageFixed inAdvisory
AlmaLinux:9openssl1:3.5.8-1.el9_8ALSA-2026:67165
AlmaLinux:9openssl-devel1:3.5.8-1.el9_8ALSA-2026:67165
AlmaLinux:9openssl-libs1:3.5.8-1.el9_8ALSA-2026:67165
AlmaLinux:9openssl-perl1:3.5.8-1.el9_8ALSA-2026:67165
Alpine:v3.21openssl3.3.7-r1ALPINE-CVE-2026-75803
Alpine:v3.22openssl3.5.8-r0ALPINE-CVE-2026-75803
Alpine:v3.23openssl3.5.8-r0ALPINE-CVE-2026-75803
Alpine:v3.24openssl3.5.8-r0ALPINE-CVE-2026-75803
Debian:12openssl3.0.22-1~deb12u1DEBIAN-CVE-2026-75803
Debian:13openssl3.5.7-1~deb13u2DEBIAN-CVE-2026-75803
Debian:14openssl3.6.4-1DEBIAN-CVE-2026-75803
Ubuntu:22.04:LTSedk22022.02-3ubuntu0.22.04.7USN-8865-1
Ubuntu:24.04:LTSedk22024.02-2ubuntu0.10USN-8865-1
Ubuntu:24.04:LTSedk22024.02-2ubuntu0.10UBUNTU-CVE-2026-75803
Ubuntu:26.04:LTSedk22025.11-3ubuntu7.3UBUNTU-CVE-2026-75803
Ubuntu:26.04:LTSedk22025.11-3ubuntu7.3USN-8865-1
Ubuntu:26.10edk2no fix listedUBUNTU-CVE-2026-75803
Ubuntu:26.04:LTSedk2-hweno fix listedUBUNTU-CVE-2026-75803
Ubuntu:26.10edk2-hweno fix listedUBUNTU-CVE-2026-75803
Ubuntu:22.04:LTSopenssl3.0.2-0ubuntu1.29USN-8678-1
Ubuntu:22.04:LTSopenssl3.0.2-0ubuntu1.29UBUNTU-CVE-2026-75803
Ubuntu:24.04:LTSopenssl3.0.13-0ubuntu3.15USN-8678-1
Ubuntu:24.04:LTSopenssl3.0.13-0ubuntu3.15UBUNTU-CVE-2026-75803
Ubuntu:26.04:LTSopenssl3.5.5-1ubuntu3.5USN-8678-3
Ubuntu:26.04:LTSopenssl3.5.5-1ubuntu3.4USN-8678-1
Ubuntu:26.04:LTSopenssl3.5.5-1ubuntu3.5UBUNTU-CVE-2026-75803

Affected products (as reported)

VendorProductVersions
OpenSSL OpenSSL 4.0.0 – before 4.0.23.6.0 – before 3.6.43.5.0 – before 3.5.83.4.0 – before 3.4.73.0.0 – before 3.0.22

Weakness: CWE-354 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

References