OpenSSL DANE TLSA UAF Vulnerability
CVE-2026-28387 Published on April 7, 2026
Potential Use-after-free in DANE Client Code
Issue summary: An uncommon configuration of clients performing DANE TLSA-based
server authentication, when paired with uncommon server DANE TLSA records, may
result in a use-after-free and/or double-free on the client side.
Impact summary: A use after free can have a range of potential consequences
such as the corruption of valid data, crashes or execution of arbitrary code.
However, the issue only affects clients that make use of TLSA records with both
the PKIX-TA(0/PKIX-EE(1) certificate usages and the DANE-TA(2) certificate
usage.
By far the most common deployment of DANE is in SMTP MTAs for which RFC7672
recommends that clients treat as 'unusable' any TLSA records that have the PKIX
certificate usages. These SMTP (or other similar) clients are not vulnerable
to this issue. Conversely, any clients that support only the PKIX usages, and
ignore the DANE-TA(2) usage are also not vulnerable.
The client would also need to be communicating with a server that publishes a
TLSA RRset with both types of TLSA records.
No FIPS modules are affected by this issue, the problem code is outside the
FIPS module boundary.
Vulnerability Analysis
CVE-2026-28387 can be exploited with network access, and does not require authorization privileges or user interaction. This vulnerability is consided to have a high level of attack complexity. The potential impact of an exploit of this vulnerability is considered to be very high.
Weakness Type
What is a Dangling pointer Vulnerability?
Referencing memory after it has been freed can cause a program to crash, use unexpected values, or execute code.
CVE-2026-28387 has been classified to as a Dangling pointer vulnerability or weakness.
Products Associated with CVE-2026-28387
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Affected Versions
OpenSSL:- Version 3.6.0 and below 3.6.2 is affected.
- Version 3.5.0 and below 3.5.6 is affected.
- Version 3.4.0 and below 3.4.5 is affected.
- Version 3.3.0 and below 3.3.7 is affected.
- Version 3.0.0 and below 3.0.20 is affected.
- Version 1.1.1 and below 1.1.1zg is affected.
- Before V5.0 is affected.
- Before * is affected.
Exploit Probability
EPSS (Exploit Prediction Scoring System) scores estimate the probability that a vulnerability will be exploited in the wild within the next 30 days. The percentile shows you how this score compares to all other vulnerabilities.