CVE-2026-55964Network attack vector

Certificate trust bypass via temporary-CA key-usage exemption

Published Jun 25, 2026 · Updated Jun 25, 2026

Improper certificate validation in wolfSSL 5.7.4 through 5.9.1 allows remote attackers to bypass certificate trust checks. X509_verify_cert exempts chain-supplied WOLFSSL_TEMP_CA intermediates from keyCertSign enforcement when a Key Usage extension is present. Exposure requires an OpenSSL-compatibility build without ALLOW_INVALID_CERTSIGN that processes attacker-supplied intermediates; exploitation lets an unauthorized intermediate sign an accepted chain.

CVSS severity6.3
Medium
EPSS probability0.19%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper certificate validation in wolfSSL 5.7.4 through 5.9.1 allows remote attackers to bypass certificate trust checks. X509_verify_cert exempts chain-supplied WOLFSSL_TEMP_CA intermediates from keyCertSign enforcement when a Key Usage extension is present. Exposure requires an OpenSSL-compatibility build without ALLOW_INVALID_CERTSIGN that processes attacker-supplied intermediates; exploitation lets an unauthorized intermediate sign an accepted chain.

The record

CVE
CVE-2026-55964
Published
Jun 25, 2026
Updated
Jun 25, 2026
Vendor
wolfSSL
Product
wolfSSL
Classifications
CWE-295, T1553
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jun 25, 2026CVE publishedPublication date reported by the CVE source.
  2. Jun 25, 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=5.7.4 <=5.9.1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

wolfSSL · wolfSSLversion=5.7.4 <=5.9.1

Published CVSS scores

6.3wolfSSL Inc.CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N
5.3NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N

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-295Improper Certificate Validation
T1553Subvert Trust Controls

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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