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OpenSSL CVE-2026-28389

| EUVDEUVD-2026-19965 HIGH
NULL Pointer Dereference (CWE-476)
2026-04-07 openssl GHSA-7x88-9hgc-69gf
Denial Of Service Null Pointer Dereference OpenSSL
High
Disputed · 7.5 NVD
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Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata – not a confirmed exploit chain

  1. Access
    Send crafted CMS EnvelopedData message
  2. Delivery
    KeyAgreeRecipientInfo processing triggered
  3. Exploit
    Missing optional parameters field accessed
  4. Execution
    NULL pointer dereference occurs
  5. Impact
    Application crashes

Vulnerability Assessment

Weakness
CWE
CWE-476
OWASP Top 10:2025
A10:2025 - Mishandling of Exceptional Conditions
ASVS 5.0
V16 - Security Logging and Error Handling Null pointer safety, defensive checks
MITRE ATT&CK

1 technique across 1 tactic: Impact

The technique list with ATT&CK links and the kill-chain view is part of the Basic plan and up.

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Exploitation Conditions

Remote unauthenticated attacker sends crafted CMS EnvelopedData message with KeyAgreeRecipientInfo lacking optional parameters field in KeyEncryptionAlgorithmIdentifier. Affects applications processing untrusted CMS data before authentication. No victim interaction required.
Impact

CVSS 7.5 reflects unauthenticated network DoS via malformed CMS messages. EPSS 0.03% indicates low observed exploitation activity. Impact is service availability only; no confidentiality or integrity compromise. Priority depends on exposure: critical for S/MIME processors and CMS-based protocols handling untrusted input, lower for internal-only deployments. Vendor patches available across all affected OpenSSL versions.
Exploit ScenarioDerived

Attacker sends crafted CMS EnvelopedData message with KeyAgreeRecipientInfo lacking optional KeyEncryptionAlgorithmIdentifier parameters to application calling CMS_decrypt(). NULL pointer dereference crashes service before authentication checks. No complexity required; network-accessible CMS processors are direct targets.
Act Now Prioritize within 24-48h. Why: Active threat signals + CRITICAL/HIGH severity.
Patch available 0.0% exploitation probability (EPSS)

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AnalysisAIv1 – Apr 07, 2026

Null pointer dereference in OpenSSL 1.0.2 through 3.6 CMS EnvelopedData processing crashes applications before authentication when KeyAgreeRecipientInfo messages lack optional parameters field. Unauthenticated remote attackers can trigger denial of service against S/MIME processors and CMS-based protocol handlers calling CMS_decrypt() on untrusted input. FIPS modules unaffected. Vendor-released patches available for all affected branches (1.0.2zp, 1.1.1zg, 3.0.20, 3.3.7, 3.4.5, 3.5.6, 3.6.2). Low observed exploitation activity; no public exploit identified at time of analysis.

RemediationAI

Vendor-released patch: upgrade to OpenSSL 1.0.2zp, 1.1.1zg, 3.0.20, 3.3.7, 3.4.5, 3.5.6, or 3.6.2 per affected version branch. Upstream fixes available via commits f80f83bc5fd0, 16cea4188e0e, 785cbf7ea3b5, c6725634e089, 7b5274e81240. No workarounds identified; patching required. Prioritize internet-facing S/MIME gateways and services processing untrusted CMS data. Verify FIPS module usage if applicable (unaffected by this issue). Consult vendor advisory https://openssl-library.org/news/secadv/20260407.txt and Ubuntu security notice https://ubuntu.com/security/notices/USN-8155-1 for distribution-specific guidance. Validate patch deployment through regression testing of CMS EnvelopedData workflows.

Affected VersionsENISA

OpenSSL 1.0.2 <1.0.2zp
OpenSSL 3.6.0 <3.6.2
OpenSSL 3.4.0 <3.4.5
OpenSSL 3.0.0 <3.0.20
OpenSSL 3.5.0 <3.5.6
OpenSSL 3.3.0 <3.3.7
OpenSSL 1.1.1 <1.1.1zg

Affected Packages

euvd openssl fix: 1.0.2zp, 1.1.1zg, 3.0.20, 3.3.7, 3.4.5, 3.5.6, 3.6.2

Source: OSV (Open Source Vulnerabilities)

Affects your stack

Affects 1 package in euvd

Checking this CVE against your own stacks and servers is part of the Basic plan and up.

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Technical ContextAI · show details

CWE-476 null pointer dereference occurs when CMS_decrypt() processes KeyEncryptionAlgorithmIdentifier within KeyAgreeRecipientInfo structures. Code unconditionally accesses optional parameters field without null-check validation. Failure occurs pre-authentication during ASN.1 parsing phase before cryptographic operations, enabling low-complexity network-based exploitation without privileges or user interaction per CVSS:3.1/AV:N/AC:L/PR:N/UI:N.

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  • Exploit and PoC references, threat intelligence from 22 sources
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Severity by source

Sources disagree (Low–High)
NVD PRIMARY 7.5 HIGH
AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
SUSE HIGH
Red Hat 5.9 LOW

vuln.today treats the vendor’s rating as authoritative. A higher third-party CVSS (e.g. CISA-ADP) is shown for transparency but does not drive the headline severity.

CVSS VectorNVD

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

Lifecycle Timeline

2
Patch released
Apr 07, 2026 - 22:16 nvd
Patch available
CVE Published
Apr 07, 2026 - 22:00 nvd
HIGH 7.5

DescriptionNVD

Issue summary: During processing of a crafted CMS EnvelopedData message with KeyAgreeRecipientInfo 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 a CMS EnvelopedData message that uses KeyAgreeRecipientInfo is processed, the optional parameters field of KeyEncryptionAlgorithmIdentifier 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.

Executive ViewAI

Why It Matters

OpenSSL versions 1.0.2 through 3.6 contain a null pointer dereference in CMS EnvelopedData processing that allows unauthenticated attackers to crash S/MIME and CMS-enabled applications, disrupting email security and encrypted communication services. Organizations using affected OpenSSL versions in email systems, secure messaging platforms, or certificate-based protocols face operational availability risks without immediate patching.

Business Impact: High
Compensating Controls

Apply vendor patch. Until patching is complete: disable CMS_decrypt() processing of untrusted EnvelopedData messages where feasible, implement network-level filtering to restrict malicious CMS messages, and monitor for abnormal application crashes correlated with email or encrypted message receipt.

Threat Intelligence Overview

EPSS Score
0.0%
Top 92% exploitable
Threat Intel
1
1 source
Social Media
1
Sightings
Data Quality
9 sources
Confidence: High
EUVD NVD CVE.org EPSS Vulnrichment CISA Vendor CIRCL GitHub VulDB

How this decision was reached

The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.

SignalValue
Severity HIGH
CISA KEV No
Public POC No
EPSS 0.0%
Patch available Yes
Active threat Yes
Deciding rule
Active threat signals + CRITICAL/HIGH severity
What every action level means
Emergency Immediate action required. Criteria: CRITICAL + in CISA KEV (actively exploited) without patch, OR CRITICAL + EPSS > 30% without patch, OR CRITICAL + active threat signals without patch.
Act Now Prioritize within 24-48h. Criteria: in KEV with patch available, OR CRITICAL + public POC, OR HIGH + EPSS > 10%, OR CRITICAL + active threat, OR any CRITICAL severity.
This Week Schedule remediation this week. Criteria: HIGH severity (CVSS 7.0-8.9). Patch within normal change window.
This Month Plan within 30 days. Criteria: MEDIUM severity (CVSS 4.0-6.9), lower exploitation probability. Include in regular patch cycle.
Monitor Track and reassess. Criteria: LOW severity (CVSS 0.1-3.9), minimal exploitation risk. No immediate action needed.

SSVC AssessmentENISA

SSVC Decision
Scheduled
Exploitation
None
System Exposure· derived
Open
Automatable
Yes
Human Impact
High
Technical Impact
Partial

Priority Score

48
Low Medium High Critical
KEV: 0
EPSS: 0
CVSS: +38
PoC: 0
Weaponized: 0
Threat intel: +10
Gov advisory: 0

Attack Technique

Null Pointer Dereference MEDIUM

A null pointer dereference occurs when a program attempts to access memory through a pointer that has been set to NULL (address 0x0).

Denial of Service MEDIUM

Denial of Service attacks render applications or systems unavailable by overwhelming resources or triggering failure conditions.

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Same weakness CWE-476 – NULL Pointer Dereference

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Same technique Denial Of Service

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CVE-2011-0609 HIGH POC
7.8

Vendor StatusVendor

SUSE

Severity: High
Product Status
Container suse/ltss/sle12.5/sles12sp5:8.5.219 Affected
Container suse/manager/4.3/proxy-httpd:4.3.17.9.76.9 Container suse/manager/4.3/proxy-squid:4.3.17.9.75.7 Container suse/manager/4.3/proxy-ssh:4.3.17.9.66.7 Affected
Container suse/manager/4.3/proxy-salt-broker:4.3.17.9.66.9 Container suse/manager/4.3/proxy-tftpd:4.3.17.9.66.8 Affected
Container suse/sl-micro/6.0/baremetal-os-container:2.1.3-6.157 Container suse/sl-micro/6.0/kvm-os-container:2.1.3-6.141 Container suse/sl-micro/6.0/rt-os-container:2.1.3-7.155 Affected
Container suse/sl-micro/6.0/base-os-container:2.1.3-7.124 Image SL-Micro Image SLE-Micro Image SLE-Micro-Azure Image SLE-Micro-BYOS Image SLE-Micro-BYOS-Azure Image SLE-Micro-BYOS-EC2 Image SLE-Micro-BYOS-GCE Image SLE-Micro-EC2 Image SLE-Micro-GCE Affected

Threat IntelligenceMISP

CISA Advisories
ICSA-26-134-10
Sources: CISA (public domain)

References

Advisories & patches
PATCH https://github.com/openssl/openssl/commit/16cea4188e0ea567deb4f93f85902247e67384f5 PATCH https://github.com/openssl/openssl/commit/785cbf7ea3b5a6f5adf0c1ccb92b79d89c35c616 PATCH https://github.com/openssl/openssl/commit/7b5274e812400cacb6f3be4c2df5340923fa807f PATCH https://github.com/openssl/openssl/commit/c6725634e089eb2b634b10ede33944be7248172a PATCH https://github.com/openssl/openssl/commit/f80f83bc5fd036bc47d773e8b15a001e2b4ce686 ADVISORY https://nvd.nist.gov/vuln/detail/CVE-2026-28389 ADVISORY https://openssl-library.org/news/secadv/20260407.txt ADVISORY https://ubuntu.com/security/notices/USN-8155-1 ADVISORY https://vuldb.com/vuln/355905 ADVISORY https://www.suse.com/support/update/SUSE-SU-2026:1213/ ADVISORY https://www.suse.com/support/update/SUSE-SU-2026:1214/ ADVISORY https://www.suse.com/support/update/SUSE-SU-2026:1215/ ADVISORY https://www.suse.com/support/update/SUSE-SU-2026:1216/ ADVISORY https://www.suse.com/support/update/SUSE-SU-2026:1255/ ADVISORY https://www.suse.com/support/update/SUSE-SU-2026:1256/ ADVISORY https://www.suse.com/support/update/SUSE-SU-2026:1257/ ADVISORY https://www.suse.com/support/update/SUSE-SU-2026:1290/ ADVISORY https://www.suse.com/support/update/SUSE-SU-2026:1291/ ADVISORY https://www.suse.com/support/update/SUSE-SU-2026:1375/ ADVISORY https://www.suse.com/support/update/SUSE-SU-2026:1386/ ADVISORY https://www.suse.com/support/update/SUSE-SU-2026:21037/ ADVISORY https://www.suse.com/support/update/SUSE-SU-2026:21065/ ADVISORY https://www.suse.com/support/update/SUSE-SU-2026:21107/ REF https://cert-portal.siemens.com/productcert/html/ssa-032379.html REF https://cert-portal.siemens.com/productcert/html/ssa-265688.html

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