High

NULL Dereference in OpenSSL CMS KeyAgreeRecipientInfo Processing

IdentifiersCVE-2026-28389CWE-476· NULL Pointer Dereference

CVE-2026-28389 is a NULL pointer dereference vulnerability in OpenSSL's CMS EnvelopedData processing path. When processing a crafted CMS EnvelopedData message containing KeyAgreeRecipientInfo, OpenSSL examines the optional parameters field of the KeyEncryptionAlgorithmIdentifier 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 is reachable in applications or services that invoke CMS_decrypt() on attacker-controlled CMS input, including S/MIME handling and other CMS-based protocols. The OpenSSL advisory describes this as occurring before authentication or cryptographic operations complete. The affected 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

What it means. What to do now. Patch path, mitigations, and the assume-compromise checklist.

Impact

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

Successful exploitation causes the vulnerable process to crash, resulting in denial of service. Based on the provided information, the impact is limited to availability loss; no confidentiality, integrity, privilege escalation, or code execution impact is indicated. Because the flaw is triggered while parsing attacker-controlled CMS data, network-reachable services such as mail gateways or other CMS-consuming applications may be forced to terminate or fail request processing.

Mitigation

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

Until patched, reduce exposure by avoiding or restricting processing of untrusted CMS EnvelopedData input, especially in code paths that call CMS_decrypt() on externally supplied data such as S/MIME or CMS-based protocol messages. Where feasible, gate CMS parsing behind trust boundaries, input validation, or service isolation to limit denial-of-service impact. No specific vendor workaround beyond upgrading is provided in the supplied content.

Remediation

Patch, then assume compromise.

Upgrade OpenSSL to a fixed release. The provided content states that fixes are included in OpenSSL 3.6.2, 3.5.6, 3.4.5, 3.3.7, 3.0.20, and in premium-support releases 1.1.1zg and 1.0.2zp where applicable. Downstream consumers should apply the corresponding vendor security update if OpenSSL is bundled by the operating system or application.

PUBLIC EXPLOITS

Exploits

No public exploits tracked yet. Mallory keeps watching.

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 FoundationOpensslapplication

Vendor-confirmed product mapping. Mallory continuously reconciles this list against your asset inventory.

ACTIVITY FEED

Recent activity

15 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.

15 SOURCESView more in app

alpinelinuxNews

Apr 15, 2026

Alpine Linue stable releases 3.20.10, 3.21.7, 3.22.4, 3.23.4 | Alpine Linux

A specific vulnerability in OpenSSL addressed in Alpine Linux stable releases 3.20.10, 3.21.7, 3.22.4, and 3.23.4.

help net securityNews

Apr 8, 2026

OpenSSL 3.6.2 lands with eight CVE fixes - Help Net Security

A NULL dereference bug in CMS KeyAgreeRecipientInfo processing in OpenSSL.

cyberthroneNews

Apr 8, 2026

OpenSSL 3.6.2: The Moderate Severity Wave - TheCyberThrone

A NULL pointer dereference in CMS KeyAgreeRecipientInfo processing that can crash applications handling malformed CMS/S/MIME content.

openssl libraryNews

Apr 7, 2026

OpenSSL Release Announcement for 3.6.2, 3.5.6, 3.4.5, 3.3.7, 3.0.20, 1.1.1zg and 1.0.2zp | OpenSSL Library

Possible NULL dereference when processing CMS KeyAgreeRecipientInfo in OpenSSL.

+1 more in the timeline

What this page doesn’t show

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Exposure mapping

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Threat actor evidence

Every observed campaign linking this CVE to a named adversary.

Associated malware

Malware families riding this exploit, with evidence and IOCs.

Detection signatures

YARA, Sigma, Snort, and vendor rules, auto-deployed to your SIEM.

Vendor-by-vendor mapping

Cross-references every affected SKU, including bundled OEM variants.

Social activity9