CVE-2026-28387Network attack vector

Client memory corruption via mismatched X509 deallocation

Published Apr 7, 2026 · Updated Apr 7, 2026

Use-after-free in OpenSSL DANE client authentication allows remote attackers to crash or corrupt client processes via TLSA records. The dane_match_cert function releases dane->mcert with OPENSSL_free instead of the reference-aware X509_free operation. Reachability requires a client accepting both PKIX and DANE-TA usages and a server publishing both record types; the vendor identifies data corruption, crashes, and arbitrary code execution as consequences.

CVSS severity8.1
High
EPSS probability0.67%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Use-after-free in OpenSSL DANE client authentication allows remote attackers to crash or corrupt client processes via TLSA records. The dane_match_cert function releases dane->mcert with OPENSSL_free instead of the reference-aware X509_free operation. Reachability requires a client accepting both PKIX and DANE-TA usages and a server publishing both record types; the vendor identifies data corruption, crashes, and arbitrary code execution as consequences.

The record

CVE
CVE-2026-28387
Published
Apr 7, 2026
Updated
Apr 7, 2026
Vendor
OpenSSL Project
Product
OpenSSL
Classifications
CWE-416, T1203
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Apr 7, 2026CVE publishedPublication date reported by the CVE source.
  2. Apr 7, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=1.1.1 <1.1.1zg
  2. Affected versionversion=3.0.0 <3.0.20
  3. Affected versionversion=3.3.0 <3.3.7
  4. Affected versionversion=3.4.0 <3.4.5
  5. Affected versionversion=3.5.0 <3.5.6
  6. Affected versionversion=3.6.0 <3.6.2

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

OpenSSL Project · OpenSSLversion=1.1.1 <1.1.1zg; version=3.0.0 <3.0.20; version=3.3.0 <3.3.7; version=3.4.0 <3.4.5; version=3.5.0 <3.5.6; version=3.6.0 <3.6.2

Published CVSS scores

8.1CISA ADPCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-416Use After Free
T1203Exploitation for Client Execution

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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