# CVE-2026-28387: OpenSSL use-after-free in DANE TLSA-based authentication

Source: https://junglewise.ai/threats/cve-2026-28387-openssl-use-after-free-in-dane-tlsa-based-authentication  
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-2026-28387 · Severity: high · CVSS 8.1 · Published 2026-04-07

OpenSSL is a widely used security library that enables encrypted communications for websites and email servers. A vulnerability exists in how certain clients verify server identities using DANE TLSA records, which could allow an attacker to crash the application or potentially execute malicious code. This issue primarily affects specialized configurations; standard email (SMTP) clients following common security standards are generally not at risk.

Technologies: [OpenSSL](https://junglewise.ai/threats/technologies/openssl), [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: [OpenSSL](https://junglewise.ai/threats/vendors/openssl), [Siemens](https://junglewise.ai/threats/vendors/siemens).

## Quick answers

**Is CVE-2026-28387 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-28387 being exploited in the wild.

**How severe is CVE-2026-28387?** High severity, with a CVSS score of 8.1, published 7 April 2026.

**Which products and versions are affected?** OpenSSL 1.1.1 to 1.1.1zg, 3.0.0 to 3.0.19, 3.3.0 to 3.3.6, 3.4.0 to 3.4.4, 3.5.0 to 3.5.5, 3.6.0 to 3.6.1, 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; Siemens SIMATIC CN 4100 < V5.0; Siemens SIMATIC S7-1500 TM MFP - GNU/Linux subsystem All versions.

**Is there a fix for CVE-2026-28387?** A patch was published on 2026-03-05: Fixes merged into OpenSSL source code. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-28387 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-28387?** Check whether you run OpenSSL, 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 use-after-free and double-free vulnerability exists in OpenSSL's 'dane_match_cert' function within 'crypto/x509/x509_vfy.c'. The root cause is the use of 'OPENSSL_free' instead of 'X509_free' on an X509 object, leading to incorrect reference counting and memory management. The vulnerability is triggered when a client using DANE TLSA-based authentication encounters a server publishing a TLSA RRset containing both PKIX-TA(0)/PKIX-EE(1) and DANE-TA(2) certificate usages. Successful exploitation could lead to data corruption, denial of service, or arbitrary code execution. The issue is patched in OpenSSL versions 3.6.2, 3.5.6, 3.4.5, 3.3.7, and 3.0.20.

## 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
- Siemens SIMATIC CN 4100 < V5.0
- Siemens SIMATIC S7-1500 TM MFP - GNU/Linux subsystem All versions

## Timeline

- 2026-03-05: patched: Fixes merged into OpenSSL source code.
- 2026-04-07: advisory: OpenSSL Security Advisory published.
- 2026-04-07: disclosed: CVE-2026-28387 published.

## References

- [https://github.com/openssl/openssl/commit/07e727d304746edb49a98ee8f6ab00256e1f012b](https://github.com/openssl/openssl/commit/07e727d304746edb49a98ee8f6ab00256e1f012b)
- [https://github.com/openssl/openssl/commit/258a8f63b26995ba357f4326da00e19e29c6acbe](https://github.com/openssl/openssl/commit/258a8f63b26995ba357f4326da00e19e29c6acbe)
- [https://github.com/openssl/openssl/commit/444958deaf450aea819171f97ae69eaedede42c3](https://github.com/openssl/openssl/commit/444958deaf450aea819171f97ae69eaedede42c3)
- [https://github.com/openssl/openssl/commit/7a4e08cee62a728d32e60b0de89e6764339df0a7](https://github.com/openssl/openssl/commit/7a4e08cee62a728d32e60b0de89e6764339df0a7)
- [https://github.com/openssl/openssl/commit/ec03fa050b3346997ed9c5fef3d0e16ad7db8177](https://github.com/openssl/openssl/commit/ec03fa050b3346997ed9c5fef3d0e16ad7db8177)
- [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)

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