What is CVE-2026-75803?

CVE-2026-75803 is AEAD Forgeries with Empty Ciphertext When Using EVP_Cipher(). The supplied enrichment data classifies it as Unclassified mapped to CWE-354 CWE-354.

Which versions are affected?

Affected product and version evidence is listed in the product table above. Current public advisories should be checked for exact version scope before patch targeting is finalized.

Is there active exploitation?

Active exploitation is not confirmed from current sources for CVE-2026-75803. If exploitation is not confirmed from current sources, teams should document that status and continue monitoring KEV, vendor, and telemetry updates.

No. CVE-2026-75803 is not listed in CISA KEV in the supplied enrichment data. KEV status should be monitored because it can change after initial disclosure or after exploitation becomes publicly confirmed.

Is there a public exploit?

A public PoC is not confirmed from current sources for CVE-2026-75803. Public exploit or PoC availability should raise triage priority, especially for exposed or business-critical systems.

How can defenders detect it?

Start with Not reported where available. Look for vulnerability-class behavior, product errors, suspicious authentication events, exploit probes, and abnormal process activity based only on evidence that applies to the affected product.

How should teams prioritize it?

Prioritize CVE-2026-75803 using CVSS null, EPSS 0%, KEV status, public PoC status, and asset exposure. Internet-facing, privileged, or business-critical deployments should be handled first.

Are workarounds available?

The supplied mitigation guidance says to apply vendor patches and restrict external exposure until fixed. Fixed-version evidence is listed in the mitigation section above.

Which threat actors are linked publicly?

No public threat actor linkage is confirmed from current sources. Do not attribute exploitation to a threat actor unless the source evidence explicitly supports that linkage.

What should be done in the next 24 hours?

Identify exposed assets running affected vendor/product/version combinations. Prioritize based on EPSS, PoC availability, and external exposure. Search available logs for exploit probes, errors, authentication anomalies, or suspicious child processes matching the vulnerability class. Open remediation tickets with affected assets, owners, evidence status, and detection coverage so decisions are traceable.

CVE-2026-75803

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

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 Aug 25, 2026Updated Aug 25, 2026Sources: NVD, OpenSSL (CNA), GitHub, SOCRadar CTI

Triage

Is it exploited, how likely is exploitation, what does it touch, and how severe do the scoring sources call it.

Exploitation

Unreported

no source claims exploitation

EPSS

ahead of 0% of scored CVEs

Affects

OpenSSL

5 products listed

CVSS base

Unscored

no source published a base score

Remediation

The vendor's own words where we have them.

Upgrade OpenSSL to a fixed release. Apply vendor patches per advisory and restrict external exposure of the affected component until patched.

First 24 hours

Ordered from the record's own fields — exposure first, because you cannot patch what you have not found.

Identify exposed assets running affected vendor/product/version combinations.
Prioritize based on EPSS, PoC availability, and external exposure.
Search available logs for exploit probes, errors, authentication anomalies, or suspicious child processes matching the vulnerability class.

Affected scope

Vendor, product and version as the advisories word them.

Vendor	Product	Versions	Status
OpenSSL	OpenSSL	4.0.0 to < 4.0.2	Vulnerable
OpenSSL	OpenSSL	3.6.0 to < 3.6.4	Vulnerable
OpenSSL	OpenSSL	3.5.0 to < 3.5.8	Vulnerable
OpenSSL	OpenSSL	3.4.0 to < 3.4.7	Vulnerable
OpenSSL	OpenSSL	3.0.0 to < 3.0.22	Vulnerable

What this weakness leads to

MITRE's own consequences and mitigations for the weakness class — the authority's wording, not guidance derived from the CVSS vector.

MITRE

CWE-354 · Improper Validation of Integrity Check Value

Modify Application Data
Other
Hide Activities

Mitigation: Ensure that the checksums present in messages are properly checked in accordance with the protocol specification before they are parsed and used.::

Weakness & attack patterns

CWE-354

Attack patterns reported against this CVE. The ATT&CK techniques below are inferred from its weakness class.

CAPEC-463 · Padding Oracle Crypto AttackCAPEC-145 · Checksum SpoofingCAPEC-75 · Manipulating Writeable Configuration Files

Timeline

What happened to this CVE, newest first — with the readings a source repeats on a schedule counted underneath rather than listed.

2026
Initial · CVE published
Aug 25, 2026 · NVD

References

6 on the record

github.com/openssl/openssl/commit/119ab9555dc62275bbd71f6f49529b1a44feba42
Exploit, Third Party Advisory, Mitre
github.com/openssl/openssl/commit/3621257986e27e540bf96a11570929a6e5a9e05b
Exploit, Third Party Advisory, Mitre
github.com/openssl/openssl/commit/6c7aa6f8f6449b7fe0137ee8be65fcd239bd7d6a
Exploit, Third Party Advisory, Mitre
github.com/openssl/openssl/commit/bdeb0cd994d915342787f117ee75044f0dc36f34
Exploit, Third Party Advisory, Mitre
github.com/openssl/openssl/commit/bf95f5f772e9362f87b25cfa2f8cb15d984865b9
Exploit, Third Party Advisory, Mitre
openssl-library.org/news/secadv/20260825.txt
Vendor Advisory, Mitre

Elsewhere on this site

OpenSSLevery CVE for this vendor
Unclassifiedsame class
CWE-354other pages naming this weakness

Not in any source we poll

Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.

No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
No exploit packet captures, log samples, or incident case IDs supplied.

Answered from this record1

What should defenders know first?

CVE-2026-75803 is AEAD Forgeries with Empty Ciphertext When Using EVP_Cipher(), a unscored vulnerability affecting OpenSSL from OpenSSL. The current evidence does not list it in CISA KEV, and the exploit status is: Active exploitation is not confirmed from current sources for CVE-2026-75803. Public exploit evidence is: A public PoC is not confirmed from current sources for CVE-2026-75803. The affected-version evidence is listed in the key facts and affected products tables. Defenders should first verify whether exposed or business-critical assets run those versions, then apply vendor patches or mitigations, restrict reachable attack surface, and preserve logs for detection review. CVSS null describes technical severity, while EPSS 0% helps estimate near-term exploit likelihood; neither replaces asset context. Unknown fields should remain explicit in tickets, and threat actor, IOC, victimology, or payload claims should not be added unless a cited source supports them. Monitor CISA KEV, vendor advisories, NVD changes, public PoC repositories, and internal telemetry for update triggers.