CVE-2022-1343 is a medium-severity vulnerability in OpenSSL versions 3.0.0, 3.0.1, and 3.0.2, fixed in version 3.0.3. The flaw resides in the OCSP (Online Certificate Status Protocol) response verification function, specifically in `OCSP_basic_verify`. This function is responsible for verifying the signer certificate on an OCSP response, which is critical for validating the revocation status of X.509 certificates. The vulnerability arises when the non-default flag `OCSP_NOCHECKS` is used. Under this condition, the function incorrectly returns a positive verification result even if the signer certificate fails verification. Normally, without this flag, a certificate verification failure results in a negative return value indicating a fatal error, or zero for a non-fatal failure. The incorrect positive result can lead to acceptance of potentially invalid or malicious OCSP responses. This issue also affects the OpenSSL command-line "ocsp" application when used with the `-no_cert_checks` option. In this case, the application reports successful verification despite verification failures, although contradictory error messages are also displayed. The vulnerability is classified under CWE-295 (Improper Certificate Validation), which can undermine trust in certificate-based authentication and revocation checking mechanisms. Exploitation does not require user interaction or privileges and can be performed remotely by an attacker who can supply crafted OCSP responses. The CVSS v3.1 base score is 5.3 (medium), reflecting the lack of confidentiality impact but potential integrity impact due to acceptance of invalid OCSP responses. No known exploits are reported in the wild. The vulnerability primarily affects systems relying on OpenSSL 3.0.x for OCSP verification, which is widely used in TLS implementations and certificate validation processes.

For European organizations, this vulnerability can undermine the integrity of certificate revocation checks, potentially allowing attackers to bypass revocation status verification of TLS certificates. This could facilitate man-in-the-middle (MITM) attacks, interception, or impersonation by accepting revoked or fraudulent certificates as valid. Critical infrastructure, financial institutions, government agencies, and enterprises relying on OpenSSL 3.0.x for secure communications and certificate validation are at risk. The impact is particularly significant in sectors where strict certificate validation is mandatory for compliance with regulations such as GDPR and eIDAS. Although the vulnerability does not affect confidentiality directly, the integrity compromise can lead to unauthorized data access or manipulation. The lack of known exploits reduces immediate risk, but the presence of this flaw in a core cryptographic library means that any future exploit could have widespread consequences. Additionally, the incorrect success indication in the OpenSSL command-line tool could mislead administrators during manual OCSP response verification, potentially causing misconfigurations or overlooked security issues.

European organizations should promptly upgrade all OpenSSL 3.0.x deployments to version 3.0.3 or later, where this vulnerability is fixed. For environments where immediate upgrade is not feasible, avoid using the `OCSP_NOCHECKS` flag in application code and refrain from using the `-no_cert_checks` option in the OpenSSL command-line tool. Review and audit any custom code or third-party software that interfaces with OpenSSL's OCSP verification to ensure it does not rely on these unsafe flags. Implement additional OCSP response validation layers or alternative revocation checking mechanisms, such as CRL (Certificate Revocation Lists) or OCSP stapling, to reduce reliance on vulnerable verification paths. Security teams should also enhance monitoring for anomalous certificate validation failures or unexpected OCSP response acceptance. Finally, educate system administrators about the misleading output of the OpenSSL "ocsp" tool with the `-no_cert_checks` option to prevent misinterpretation of verification results.