CVE-2021-46880Network attack vector

Authentication bypass via discarded chain-verification errors

Published Apr 14, 2023 · Updated Feb 7, 2025

Improper certificate validation in OpenBSD LibreSSL before 3.4.2 and OpenBSD 7.0 before errata 006 allows remote attackers to bypass authentication. In x509_verify(), compatibility-mode completion handling clears or fails to restore X509_STORE_CTX errors after no valid chain is found, allowing an invalid chain to return success. A network service that relies on the affected verifier for peer-certificate authentication can therefore accept a remote peer whose certificate chain did not validate.

CVSS severity9.8
Critical
EPSS probability0.57%
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 OpenBSD LibreSSL before 3.4.2 and OpenBSD 7.0 before errata 006 allows remote attackers to bypass authentication. In x509_verify(), compatibility-mode completion handling clears or fails to restore X509_STORE_CTX errors after no valid chain is found, allowing an invalid chain to return success. A network service that relies on the affected verifier for peer-certificate authentication can therefore accept a remote peer whose certificate chain did not validate.

The record

CVE
CVE-2021-46880
Published
Apr 14, 2023
Updated
Feb 7, 2025
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-295
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Apr 14, 2023CVE publishedPublication date reported by the CVE source.
  2. Feb 7, 2025Record 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

9.8CISA ADPCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
9.8NIST NVDCVSS:3.1/AV:N/AC:L/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.

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No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 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

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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