CyberSecBulletin
CVE-2026-28389NVD status: Modified

OpenSSL: NULL Pointer Dereference

Published Updated By the CyberSecBulletin desk

CVE-2026-28389 is a high-severity NULL pointer dereference vulnerability in OpenSSL, with a CVSS 3.1 base score of 7.5 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. The record lists versions 3.6.2, 3.5.6, 3.4.5 as the first without the flaw, so updating OpenSSL to one of those releases or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.84% chance of exploitation within 30 days, higher than 58% of scored CVEs.

Next patch cycle

High severity with no evidence of exploitation so far.

What to do

  1. Update OpenSSL to 3.6.2 or 3.5.6 or 3.4.5 or 3.3.7, whichever matches your release line, or a later version.
  2. Update SIMATIC CN 4100 to V5.0 or a later version.
  3. Read the advisory on openssl-library.org for workarounds and exact fixed builds.
  4. Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.

Affected products and versions

VendorProductAffected versionsFixed in
OpenSSLOpenSSL3.6.0 up to, but not including, 3.6.2; 3.5.0 up to, but not including, 3.5.6; 3.4.0 up to, but not including, 3.4.5; 3.3.0 up to, but not including, 3.3.7; 3.0.0 up to, but not including, 3.0.20; 1.1.1 up to, but not including, 1.1.1zg; 1.0.2 up to, but not including, 1.0.2zp3.6.2, 3.5.6, 3.4.5, 3.3.7, 3.0.20, 1.1.1zg
SiemensSIMATIC CN 4100before V5.0V5.0
SiemensSIMATIC S7-1500 TM MFP - GNU/Linux subsystemall versionsNot stated

Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.

How the severity score breaks down

Attack vector
NetworkCan be exploited remotely over a network, including the internet.
Attack complexity
LowNo special conditions are needed; the attack works reliably.
Privileges required
NoneNo account or login is needed.
User interaction
NoneNo action by a victim is required.
Scope
UnchangedImpact stays within the vulnerable component.
Confidentiality
NoneNo data is disclosed.
Integrity
NoneNothing can be modified.
Availability
HighThe component can be taken down completely.

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H. Scored by NVD.

Scoring systemScoreSeverityScored by
CVSS 3.17.5HighNVD
CVSS 3.17.5HighCISA (ADP)

Official description

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.

Source: the CVE record as published by its numbering authority, via NVD and CVE.org.

The underlying weakness: NULL Pointer Dereference

The product dereferences a pointer that it expects to be valid but is NULL.

How developers prevent this class of flaw

  • For any pointers that could have been modified or provided from a function that can return NULL, check the pointer for NULL before use. When working with a multithreaded or otherwise asynchronous environment, ensure that proper locking APIs are used to lock before the check, and unlock when it has finished.
  • Select a programming language that is not susceptible to these issues.
  • Check the results of all functions that return a value and verify that the value is non-null before acting upon it.

More NULL Pointer Dereference vulnerabilities (CWE-476)

Timeline

  1. CVE record published.
  2. CISA published its SSVC assessment (exploitation: none, automatable: yes, technical impact: partial).
  3. Record last changed materially (score, affected products, status or references).

References

Other vulnerabilities in OpenSSL

All OpenSSL vulnerabilities

Recent NULL Pointer Dereference vulnerabilities

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