CVE-2026-5501Public exploitNetwork attack vector

Forged leaf certificates via skipped signature verification

Published Apr 10, 2026 · Updated Apr 10, 2026

Improper certificate validation in wolfSSL 5.9.0 and earlier allows attackers to pass forged leaf certificates via crafted chains. wolfSSL_X509_verify_cert lets a CA:FALSE untrusted intermediate fall through without calling X509StoreVerifyCert for the leaf, so arbitrary signature bytes receive X509_V_OK. Exploitation requires any valid leaf certificate under a trusted root and an application that directly uses the OpenSSL compatibility API; the native TLS handshake is unaffected.

CVSS severity8.6
High
EPSS probability0.18%
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 5.9.0 and earlier allows attackers to pass forged leaf certificates via crafted chains. wolfSSL_X509_verify_cert lets a CA:FALSE untrusted intermediate fall through without calling X509StoreVerifyCert for the leaf, so arbitrary signature bytes receive X509_V_OK. Exploitation requires any valid leaf certificate under a trusted root and an application that directly uses the OpenSSL compatibility API; the native TLS handshake is unaffected.

The record

CVE
CVE-2026-5501
Published
Apr 10, 2026
Updated
Apr 10, 2026
Vendor
wolfSSL
Product
wolfSSL
Classifications
CWE-295
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Apr 10, 2026CVE publishedPublication date reported by the CVE source.
  2. Apr 10, 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=0 <=5.9.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

wolfSSL · wolfSSLversion=0 <=5.9.0

Published CVSS scores

8.1NIST NVDCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N
8.6wolfSSL Inc.CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA: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.

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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
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-295Improper Certificate Validation

Public exploit references

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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