What is CVE-2026-75803?

CVE-2026-75803 is a critical-severity vulnerability in OpenSSL, classified under Improper Validation of Integrity Check Value. CVSS score: 9.1/10. Published 2026-08-25.

How severe is CVE-2026-75803?

Critical severity. CVSS v3 base score is 9.1 out of 10.

Vulnerability in OpenSSL

CVE-2026-75803

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.

Published 2026-08-25 · last modified 2026-09-11.

CVSS v3 metric

CVSS v3 base score 9.1 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N.

EPSS exploit prediction

EPSS: 0.002 (12.9th percentile), scored 2026-10-10.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 13th percentile — 12.9% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.002 · newest: 0.002 · change: +0.000

Affected products

OpenSSL

Weakness classification (CWE)

CWE-354 — Improper Validation of Integrity Check Value

References

github.com/openssl/openssl/commit/119ab9555dc62275bbd71f6f49529b1a44feba42 (Patch, patch)
github.com/openssl/openssl/commit/3621257986e27e540bf96a11570929a6e5a9e05b (Patch, patch)
github.com/openssl/openssl/commit/6c7aa6f8f6449b7fe0137ee8be65fcd239bd7d6a (Patch, patch)
github.com/openssl/openssl/commit/bdeb0cd994d915342787f117ee75044f0dc36f34 (Patch, patch)
github.com/openssl/openssl/commit/bf95f5f772e9362f87b25cfa2f8cb15d984865b9 (Patch, patch)
openssl-library.org/news/secadv/20260825.txt (vendor-advisory, Vendor Advisory)

Frequently asked questions

What is CVE-2026-75803?: CVE-2026-75803 is a critical-severity vulnerability in OpenSSL, classified under Improper Validation of Integrity Check Value. CVSS score: 9.1/10. Published 2026-08-25.
How severe is CVE-2026-75803?: Critical severity. CVSS v3 base score is 9.1 out of 10.