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CVE IDCVE-2026-8763GitHub advisory IDGHSA-9pwp-9qqc-pr26

Bouncy Castle: Name Constraints bypass via trailing dot in rfc822Name and URI

CVE-2026-8763 (GitHub advisory GHSA-9pwp-9qqc-pr26) is a critical-severity vulnerability with a CVSS 4.0 base score of 9.3, classed as Improper Certificate Validation (CWE-295), in 4 packages, including org.bouncycastle:bc-fips (Maven) and org.bouncycastle:bcprov-jdk18on (Maven). Fixed versions: org.bouncycastle:bc-fips 1.0.2.7, 2.0.2 or 2.1.3; org.bouncycastle:bcprov-jdk18on 1.85; and 2 more packages.

Critical9.3Fix availableGitHub reviewed

Published 3 Aug 2026Updated 18 Sept 2026

9.3CriticalCVSS 4.0
CVE ID
CVE-2026-8763
GHSA ID
GHSA-9pwp-9qqc-pr26
EPSS
0.45%higher than 36% of CVEs
Weakness (CWE)
  • CWE-295Improper Certificate Validation
KEV status
Not in KEV
Published
3 Aug 2026
Updated
18 Sept 2026
Ecosystem
  • Maven
Assigned by (CNA)
bcorg

Summary

Source: OSV (GitHub advisory)

In Bouncy Castle for Java before 1.85, Name Constraints bypass via trailing dot in rfc822Name and URI. This issue also affects Bouncy Castle for Java LTS before 2.73.12, and Bouncy Castle for Java FIPS (BC-FJA) before bc-fips 1.0.2.7 (1.0.X series), 2.0.2 (2.0.X series) and 2.1.3 (2.1.X series).

Technical details

Source: GitHub Advisory Database

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/U:Amber

Critical9.3Base score from GitHub Advisory Database

Attack Vector AV
Network
Attack Complexity AC
Low
Attack Requirements AT
None
Privileges Required PR
None
User Interaction UI
None
Confidentiality (Vulnerable System) VC
High
Integrity (Vulnerable System) VI
High
Availability (Vulnerable System) VA
None
Confidentiality (Subsequent Systems) SC
None
Integrity (Subsequent Systems) SI
None
Availability (Subsequent Systems) SA
None
Provider Urgency U
Amber

CISA SSVC decision points

Exploitation
none
No public exploitation evidence
Automatable
yes
Attackers can automate this at scale
Technical impact
total
Full control of the affected system

CISA Coordinator assessment (SSVC 2.0.3) via CVE.org.

Affected packages

Source: OSV (GitHub advisory)

  • org.bouncycastle:bc-fips
    Maven
    pkg:maven/org.bouncycastle/bc-fips
    Affected versions
    < 1.0.2.7
    >= 2.0.0, < 2.0.2
    >= 2.1.0, < 2.1.3
    Fixed in
    1.0.2.7
    2.0.2
    2.1.3
    Show 13 listed versions
    • 1.0.0
    • 1.0.1
    • 1.0.2
    • 1.0.2.1
    • 1.0.2.3
    • 1.0.2.4
    • 1.0.2.5
    • 1.0.2.6
    • 2.0.0
    • 2.0.1
    • 2.1.0
    • 2.1.1
  • org.bouncycastle:bcprov-jdk18on
    Maven
    pkg:maven/org.bouncycastle/bcprov-jdk18on
    Affected versions
    < 1.85
    Fixed in
    1.85
    Show 18 listed versions
    • 1.71
    • 1.71.1
    • 1.72
    • 1.73
    • 1.74
    • 1.75
    • 1.76
    • 1.77
    • 1.78
    • 1.78.1
    • 1.79
    • 1.80
  • org.bouncycastle:bcprov-lts8on
    Maven
    pkg:maven/org.bouncycastle/bcprov-lts8on
    Affected versions
    < 2.73.12
    Fixed in
    2.73.12
    Show 12 listed versions
    • 2.73.0
    • 2.73.1
    • 2.73.10
    • 2.73.11
    • 2.73.2
    • 2.73.3
    • 2.73.4
    • 2.73.5
    • 2.73.6
    • 2.73.7
    • 2.73.8
    • 2.73.9
  • org.bouncycastle:bcprov-jdk15to18
    Maven
    pkg:maven/org.bouncycastle/bcprov-jdk15to18
    Affected versions
    < 1.85
    Fixed in
    1.85
    Show 23 listed versions
    • 1.63
    • 1.64
    • 1.65
    • 1.66
    • 1.67
    • 1.68
    • 1.69
    • 1.70
    • 1.71
    • 1.72
    • 1.73
    • 1.74

Fix

Source: OSV (GitHub advisory)

Fix available

  • org.bouncycastle:bc-fips: upgrade to 1.0.2.7, 2.0.2 or 2.1.3, depending on your release line
  • org.bouncycastle:bcprov-jdk18on: upgrade to 1.85 or later
  • org.bouncycastle:bcprov-lts8on: upgrade to 2.73.12 or later
  • org.bouncycastle:bcprov-jdk15to18: upgrade to 1.85 or later

Patch commits

  • 2c28b25Patch commitgithub.com/bcgit/bc-java

    Fix directoryName-prefix and email/URI trailing-dot name-constraint bypasses

    +64 −22 across 3 files

    • core/src/main/java/org/bouncycastle/asn1/x509/PKIXNameConstraintValidator.java+17 −22
    • docs/releasenotes.html+1 −0
    • prov/src/test/java/org/bouncycastle/jce/provider/test/PKIXNameConstraintsTest.java+46 −0

Release commits

The commits each fixed release tag points at. They usually bump the version rather than contain the fix itself.

  • 57fbd3cRelease commit1.85github.com/bcgit/bc-java

Vulnerability intelligence

References

Credits

  • Alex Gaynor in collaboration with Claude and Anthropic Researchreporter

Questions about CVE-2026-8763

What is the GHSA ID for CVE-2026-8763?
GitHub tracks CVE-2026-8763 as GHSA-9pwp-9qqc-pr26.
What is the CVSS score of CVE-2026-8763?
CVE-2026-8763 has a CVSS 4.0 base score of 9.3 (Critical), vector 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/U:Amber. Other published scores: CVSS 3.1 9.1.
Which versions are affected by CVE-2026-8763?
org.bouncycastle:bc-fips (Maven): < 1.0.2.7; >= 2.0.0, < 2.0.2; >= 2.1.0, < 2.1.3. org.bouncycastle:bcprov-jdk18on (Maven): < 1.85. org.bouncycastle:bcprov-lts8on (Maven): < 2.73.12. org.bouncycastle:bcprov-jdk15to18 (Maven): < 1.85.
How do I fix CVE-2026-8763?
Upgrade each package to its fixed version: org.bouncycastle:bc-fips 1.0.2.7, 2.0.2 or 2.1.3; org.bouncycastle:bcprov-jdk18on 1.85; org.bouncycastle:bcprov-lts8on 2.73.12; org.bouncycastle:bcprov-jdk15to18 1.85. The fix is in commit 2c28b25.
What is the Package URL (PURL) for CVE-2026-8763?
The affected packages' PURLs are pkg:maven/org.bouncycastle/bc-fips, pkg:maven/org.bouncycastle/bcprov-jdk18on, pkg:maven/org.bouncycastle/bcprov-lts8on and pkg:maven/org.bouncycastle/bcprov-jdk15to18.
Is CVE-2026-8763 exploited in the wild?
CISA's Known Exploited Vulnerabilities catalog doesn't list CVE-2026-8763. That means no confirmed exploitation has been catalogued, not that it is safe to leave unpatched. CISA's SSVC assessment rates exploitation as "none". EPSS estimates a 0.45% chance of exploitation in the next 30 days, higher than 36% of CVEs.

Data sources

Upstream records

  • OSV (GitHub advisory)LoadedRaw JSON
  • GitHub Advisory DatabaseLoadedRaw JSON
  • OSV (CVE record)LoadedRaw JSON
  • CVE.orgLoaded
  • CISA KEV catalogLoaded

Fetched 2 days ago (13 Oct 2026, 13:23 UTC). Records refresh automatically after 24 hours.

Where each part of this page came from

Title and description
OSV (GitHub advisory)
Severity score
GitHub Advisory Database
Weakness (CWE)
GitHub Advisory Database
Affected packages
OSV (GitHub advisory)
Fix
OSV (GitHub advisory)
References
Computed by CVEminer
SSVC
CVE.org
KEV status
CISA KEV catalog
EPSS
GitHub Advisory Database

OSV and GitHub Advisory Database content is licensed CC BY 4.0. Values marked as computed or derived were calculated by CVEminer from the upstream data.