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OpenSSL CMS KeyTransportRecipientInfo NULL Pointer Dereference

IdentifiersCVE-2026-28390CWE-476· NULL Pointer Dereference

CVE-2026-28390 is a NULL pointer dereference in OpenSSL during processing of crafted CMS EnvelopedData messages that use KeyTransportRecipientInfo with RSA-OAEP encryption. When OpenSSL processes such input via CMS_decrypt(), it examines the optional parameters field of the RSA-OAEP SourceFunc algorithm identifier without first verifying that the field is present. If the parameters field is omitted, the code can dereference a NULL pointer and crash. The issue affects applications and services that decrypt attacker-controlled CMS data, including S/MIME processing and other CMS-based protocols. The OpenSSL advisory indicates the vulnerable code is outside the OpenSSL FIPS module boundary, and the FIPS modules in 3.6, 3.5, 3.4, 3.3, and 3.0 are not affected.

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ANALYST BRIEF

Impact, mitigation & remediation

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Impact

What an attacker gets, and what they’ve been doing with it.

Successful exploitation causes the target process to crash before authentication or cryptographic operations complete, resulting in denial of service. Based on the provided information, this is an availability impact only; no confidentiality, integrity, privilege escalation, or code execution impact is indicated.

Mitigation

If you can’t patch tonight, do this now.

Avoid passing untrusted CMS EnvelopedData into CMS_decrypt() until patched, especially in S/MIME gateways, mail-processing pipelines, and CMS-based protocol handlers exposed to attacker-supplied content. Where feasible, isolate or sandbox CMS parsing/decryption components and restrict unauthenticated attackers from submitting arbitrary CMS objects. The content does not provide a specific configuration workaround beyond applying fixed versions.

Remediation

Patch, then assume compromise.

Upgrade OpenSSL to a fixed release. The provided content states fixes are included in OpenSSL 3.6.2, 3.5.6, 3.4.5, 3.3.7, and 3.0.20. Premium-support branches 1.1.1 and 1.0.2 also received fixes in 1.1.1zg and 1.0.2zp, respectively. Downstream vendors such as Linux distributions may also ship backported fixes; apply the vendor-provided security update where applicable.
PUBLIC EXPLOITS

Exploits

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VALID 0 / 0 TOTALView more in app

No public exploit code observed for this vulnerability.

EXPOSURE SURFACE

Affected products & vendors

Products and vendors Mallory has correlated with this vulnerability. Open in Mallory to drill down to specific CPE configurations and version ranges.

VendorProductType
OpenSSL Software FoundationCompat-Openssl10application
OpenSSL Software FoundationOpensslapplication
Rocky LinuxCompat-Openssl11application
Rocky LinuxRocky Linuxoperating_system

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Detection signatures

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Vendor-by-vendor mapping

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Social activity12

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