# CVE-2026-28390: OpenSSL NULL pointer dereference in CMS EnvelopedData processing

Source: https://junglewise.ai/threats/cve-2026-28390-openssl-null-pointer-dereference-in-cms-envelopeddata-processing  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-04-07. Updated: 2026-07-25  
License: CC BY 4.0 with a link back

CVE-2026-28390 · Severity: high · CVSS 7.5 · Published 2026-04-07

OpenSSL is a widely used security library that enables encrypted communications for websites, email, and corporate tools. A vulnerability has been identified where a specially crafted encrypted message can cause applications using OpenSSL to crash. This results in a denial-of-service, potentially disrupting secure communications or crashing services like S/MIME email processing before they can even verify the sender's identity.

Technologies: [Siemens SIMATIC CN 4100](https://junglewise.ai/threats/technologies/simatic-cn-4100), [Siemens SIMATIC S7-1500 TM MFP - GNU/Linux subsystem](https://junglewise.ai/threats/technologies/simatic-s7-1500-tm-mfp-gnu-linux-subsystem). Vendors: [Siemens](https://junglewise.ai/threats/vendors/siemens).

## Quick answers

**Is CVE-2026-28390 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-28390 being exploited in the wild.

**How severe is CVE-2026-28390?** High severity, with a CVSS score of 7.5, published 7 April 2026.

**Which products and versions are affected?** Siemens SIMATIC CN 4100 before V5.0.

**Is there a fix for CVE-2026-28390?** A patch was published on 2026-04-06: Fixes committed to OpenSSL repository Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-28390 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-28390?** Check whether you run Siemens SIMATIC CN 4100 or Siemens SIMATIC S7-1500 TM MFP - GNU/Linux subsystem at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

A NULL pointer dereference exists in OpenSSL's CMS (Cryptographic Message Syntax) implementation, specifically within the rsa_cms_decrypt function in crypto/cms/cms_rsa.c. When processing a CMS EnvelopedData message using KeyTransportRecipientInfo with RSA-OAEP encryption, the code fails to verify the presence of the optional parameters field in the RSA-OAEP SourceFunc algorithm identifier. An unauthenticated remote attacker can exploit this by sending a malformed CMS message, causing the application to crash during the call to CMS_decrypt(). This affects various protocols relying on CMS, such as S/MIME. The issue is resolved in OpenSSL versions 3.6.2, 3.5.6, 3.4.5, 3.3.7, 3.0.20, and 1.1.1zg.

## Affected products

- OpenSSL OpenSSL 3.6.0 to 3.6.1, 3.5.0 to 3.5.5, 3.4.0 to 3.4.4, 3.3.0 to 3.3.6, 3.0.0 to 3.0.19, 1.1.1 to 1.1.1zf
- Siemens SIMATIC CN 4100 before V5.0
- Siemens SIMATIC S7-1500 TM MFP - GNU/Linux subsystem

## Timeline

- 2026-04-06: patched: Fixes committed to OpenSSL repository
- 2026-04-07: advisory: OpenSSL Security Advisory published
- 2026-04-07: disclosed: CVE-2026-28390 published

## References

- [https://github.com/openssl/openssl/commit/01194a8f1941115cd0383bfa91c736dd3993c8bc](https://github.com/openssl/openssl/commit/01194a8f1941115cd0383bfa91c736dd3993c8bc)
- [https://github.com/openssl/openssl/commit/2e39b7a6993be445fddb9fbce316fa756e0397b6](https://github.com/openssl/openssl/commit/2e39b7a6993be445fddb9fbce316fa756e0397b6)
- [https://github.com/openssl/openssl/commit/af2a5fecd3e71a29e7568f9c1453dec5cebbaff4](https://github.com/openssl/openssl/commit/af2a5fecd3e71a29e7568f9c1453dec5cebbaff4)
- [https://github.com/openssl/openssl/commit/ea7b4ea4f9f853521ba34830cbcadc970d2e0788](https://github.com/openssl/openssl/commit/ea7b4ea4f9f853521ba34830cbcadc970d2e0788)
- [https://github.com/openssl/openssl/commit/fd2f1a6cf53b9ceeca723a001aa4b825d7c7ee75](https://github.com/openssl/openssl/commit/fd2f1a6cf53b9ceeca723a001aa4b825d7c7ee75)
- [https://openssl-library.org/news/secadv/20260407.txt](https://openssl-library.org/news/secadv/20260407.txt)
- [https://cert-portal.siemens.com/productcert/html/ssa-032379.html](https://cert-portal.siemens.com/productcert/html/ssa-032379.html)

## Related threats

- [Siemens SIMATIC CN 4100 resource exhaustion via TCP SYN flood](https://junglewise.ai/threats/cve-2026-22925-siemens-simatic-cn-4100-resource-exhaustion-via-tcp-syn-flood)
- [Siemens SIMATIC CN 4100 missing authentication and resource exhaustion](https://junglewise.ai/threats/cve-2026-22924-siemens-simatic-cn-4100-missing-authentication-and-resource)
- [Linux Kernel crypto algif_aead improper memory handling](https://junglewise.ai/threats/cve-2026-31431-linux-kernel-crypto-algif-aead-improper-memory-handling)
- [OpenSSL uninitialized memory disclosure in RSASVE key encapsulation](https://junglewise.ai/threats/cve-2026-31790-openssl-uninitialized-memory-disclosure-in-rsasve-key)
- [OpenSSL heap buffer overflow in buf2hex conversion](https://junglewise.ai/threats/cve-2026-31789-openssl-heap-buffer-overflow-in-buf2hex-conversion)