CVE-2026-57826Network attack vector

Certificate impersonation via legacy intermediate CA acceptance

Published Aug 18, 2026 · Updated Aug 19, 2026

Improper certificate validation in openHiTLS 0.2.0 through 0.3.2 allows remote attackers to have an invalid certificate chain trusted. X509_CheckExt checks basicConstraints and the CA flag only for version 3 intermediates, so version 1 or 2 intermediates bypass the CA validation path. Exploitation requires a crafted chain to reach an application that relies on openHiTLS verification, allowing an unqualified intermediate to be treated as a CA.

CVSS severity9.8
Critical
EPSS probability0.21%
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 openHiTLS 0.2.0 through 0.3.2 allows remote attackers to have an invalid certificate chain trusted. X509_CheckExt checks basicConstraints and the CA flag only for version 3 intermediates, so version 1 or 2 intermediates bypass the CA validation path. Exploitation requires a crafted chain to reach an application that relies on openHiTLS verification, allowing an unqualified intermediate to be treated as a CA.

The record

CVE
CVE-2026-57826
Published
Aug 18, 2026
Updated
Aug 19, 2026
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-295, T1557
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 18, 2026CVE publishedPublication date reported by the CVE source.
  2. Aug 19, 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?

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

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
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-295Improper Certificate Validation
T1557Adversary-in-the-Middle

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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