CVE-2021-38597Network attack vector

Certificate-validation bypass via OCSP NoCheck misinterpretation

Published Aug 12, 2021 · Updated Aug 4, 2024

Certificate validation bypass in wolfSSL before 4.8.1 allows remote attackers to trigger acceptance of an unrelated OCSP responder certificate. ParseCertRelative changes verification to NO_VERIFY when an OCSP responder certificate has the NoCheck extension, even if the certificate is unrelated to the checked chain. Exposure requires OCSP-enabled TLS clients, mutual-authentication servers, or CertManager use; the bypass undermines certificate revocation checking.

CVSS severity5.9
Medium
EPSS probability0.48%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Certificate validation bypass in wolfSSL before 4.8.1 allows remote attackers to trigger acceptance of an unrelated OCSP responder certificate. ParseCertRelative changes verification to NO_VERIFY when an OCSP responder certificate has the NoCheck extension, even if the certificate is unrelated to the checked chain. Exposure requires OCSP-enabled TLS clients, mutual-authentication servers, or CertManager use; the bypass undermines certificate revocation checking.

The record

CVE
CVE-2021-38597
Published
Aug 12, 2021
Updated
Aug 4, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-345, T1557
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 12, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

4.3NIST NVDAV:N/AC:M/Au:N/C:P/I:N/A:N
5.9NIST NVDCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/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-345Insufficient Verification of Data Authenticity
T1557Adversary-in-the-Middle

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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