CVE-2026-8763Network attack vector

Certificate constraint bypass via trailing-dot hostnames

Published Aug 3, 2026 · Updated Aug 3, 2026

Improper certificate validation in affected Bouncy Castle Java editions allows attackers to bypass email and URI name constraints. PKIXNameConstraintValidator strips trailing dots for DNS names but compares rfc822Name and URI hosts without stripping them, so excluded subtrees fail to match. Exploitation requires control of a name-constrained intermediate CA and permits issuance of certificates for email or URI hosts that the constraint excludes.

CVSS severity9.3
Critical
EPSS probability0.43%
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 affected Bouncy Castle Java editions allows attackers to bypass email and URI name constraints. PKIXNameConstraintValidator strips trailing dots for DNS names but compares rfc822Name and URI hosts without stripping them, so excluded subtrees fail to match. Exploitation requires control of a name-constrained intermediate CA and permits issuance of certificates for email or URI hosts that the constraint excludes.

The record

CVE
CVE-2026-8763
Published
Aug 3, 2026
Updated
Aug 3, 2026
Vendor
Legion of the Bouncy Castle Inc.
Product
Bouncy Castle Java
Classifications
CWE-295, T1553
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 3, 2026CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 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 <1.85

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Legion of the Bouncy Castle Inc. · Bouncy Castle Javaversion=0 <1.85
Legion of the Bouncy Castle Inc. · Bouncy Castle FIPS Java APIversion=1.0.0 <1.0.2.7; version=2.0.0 <2.0.2; version=2.1.0 <2.1.3
Legion of the Bouncy Castle Inc. · Bouncy Castle Java LTSversion=2.73.0 <2.73.12

Published CVSS scores

9.3Legion of the Bouncy Castle Inc.CVSS:4.0/AV:N/AC:L/AT:N/PR:N/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
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.

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Technologies

Your stack

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Your stack

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