CVE-2026-28390
Published: 07 April 2026
Summary
CVE-2026-28390 is a high-severity NULL Pointer Dereference (CWE-476) vulnerability in Openssl Openssl. Its CVSS base score is 7.5 (High).
Operationally, exploitation aligns with the MITRE ATT&CK technique Application or System Exploitation (T1499.004); ranked in the top 47.7% of CVEs by exploit likelihood; it is not currently listed in the CISA KEV catalog.
The strongest mitigations our analysis identified are NIST 800-53 SI-2 (Flaw Remediation) and SI-10 (Information Input Validation).
Deeper analysis
CVE-2026-28390 is a NULL pointer dereference vulnerability in OpenSSL during the processing of a crafted CMS EnvelopedData message that uses KeyTransportRecipientInfo with RSA-OAEP encryption. The issue occurs because the optional parameters field of the RSA-OAEP SourceFunc algorithm identifier is examined without first checking for its presence, leading to the dereference. Applications and services that call CMS_decrypt() on untrusted input, such as those handling S/MIME processing or CMS-based protocols, are affected. OpenSSL FIPS modules in versions 3.6, 3.5, 3.4, 3.3, and 3.0 are not vulnerable, as the affected code lies outside the FIPS module boundary.
A remote attacker with network access and no privileges required can exploit this vulnerability by supplying a malicious CMS EnvelopedData message to a vulnerable application. Successful exploitation triggers a crash before any authentication or cryptographic operations complete, resulting in a denial of service. The vulnerability has a CVSS v3.1 base score of 7.5 (AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H) and is associated with CWE-476 (NULL Pointer Dereference).
Mitigation is available through patches in OpenSSL, as detailed in the following upstream commit references: https://github.com/openssl/openssl/commit/01194a8f1941115cd0383bfa91c736dd3993c8bc, https://github.com/openssl/openssl/commit/2e39b7a6993be445fddb9fbce316fa756e0397b6, https://github.com/openssl/openssl/commit/af2a5fecd3e71a29e7568f9c1453dec5cebbaff4, https://github.com/openssl/openssl/commit/ea7b4ea4f9f853521ba34830cbcadc970d2e0788, and https://github.com/openssl/openssl/commit/fd2f1a6cf53b9ceeca723a001aa4b825d7c7ee75. Security practitioners should update to a patched version of OpenSSL and review applications for exposure to untrusted CMS data.
OWASP Top 10 for Web (2025)
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-19966
Vulnerability details
Issue summary: During processing of a crafted CMS EnvelopedData message with KeyTransportRecipientInfo a NULL pointer dereference can happen. Impact summary: Applications that process attacker-controlled CMS data may crash before authentication or cryptographic operations occur resulting in Denial of Service. When…
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a CMS EnvelopedData message that uses KeyTransportRecipientInfo with RSA-OAEP encryption is processed, the optional parameters field of RSA-OAEP SourceFunc algorithm identifier is examined without checking for its presence. This results in a NULL pointer dereference if the field is missing. Applications and services that call CMS_decrypt() on untrusted input (e.g., S/MIME processing or CMS-based protocols) are vulnerable. The FIPS modules in 3.6, 3.5, 3.4, 3.3 and 3.0 are not affected by this issue, as the affected code is outside the OpenSSL FIPS module boundary.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise TechniquesAI
Why these techniques?
NULL pointer dereference in OpenSSL CMS_decrypt() on untrusted input enables remote crash/DoS with no privileges or auth required, directly matching Application or System Exploitation for Endpoint Denial of Service.
CVEs Like This One
Affected Assets
Mitigating Controls
Mitigating Controls (NIST 800-53 r5) AI
Requires timely identification, reporting, and patching of the NULL pointer dereference flaw in OpenSSL's CMS_decrypt processing of crafted EnvelopedData messages.
Mandates error handling that prevents crashes from missing optional parameters in RSA-OAEP algorithm identifiers during CMS processing.
Enforces validation of untrusted CMS EnvelopedData inputs to block malformed KeyTransportRecipientInfo structures that trigger the NULL dereference.