CyberSecBulletin
CVE-2026-8763NVD status: Analyzed

BC-JAVA: Improper Certificate Validation

Published Updated By the CyberSecBulletin desk

CVE-2026-8763 is a critical-severity improper certificate validation vulnerability in BC-JAVA from Legion of the Bouncy Castle, with a CVSS 3.1 base score of 9.1 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. The record lists version 1.85 as the first without the flaw, so updating BC-JAVA to that release or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.43% chance of exploitation within 30 days, which is low compared with other CVEs.

Patch this week

Critical severity: a successful attack would have severe impact.

What to do

  1. Update BC-JAVA to 1.85 or a later version.
  2. Update BC-LTS-JAVA to 2.73.12 or a later version.
  3. Update BC-FJA to 1.0.2.7 or 2.0.2 or 2.1.3, whichever matches your release line, or a later version.
  4. Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.

Affected products and versions

VendorProductAffected versionsFixed in
Legion of the Bouncy CastleBC-JAVAbefore 1.851.85
Legion of the Bouncy CastleBC-LTS-JAVA2.73.0 up to, but not including, 2.73.122.73.12
Legion of the Bouncy CastleBC-FJA1.0.0 up to, but not including, 1.0.2.7; 2.0.0 up to, but not including, 2.0.2; 2.1.0 up to, but not including, 2.1.31.0.2.7, 2.0.2, 2.1.3
BouncycastleBouncy Castle For Java LTS2.73.11 and earlierNot stated
BouncycastleFips Java API1.0.0 up to, but not including, 1.0.2.7; 2.0.0 up to, but not including, 2.0.2; 2.1.0 up to, but not including, 2.1.31.0.2.7, 2.0.2, 2.1.3

Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.

How the severity score breaks down

Attack vector
NetworkCan be exploited remotely over a network, including the internet.
Attack complexity
LowNo special conditions are needed; the attack works reliably.
Privileges required
NoneNo account or login is needed.
User interaction
NoneNo action by a victim is required.
Scope
UnchangedImpact stays within the vulnerable component.
Confidentiality
HighAll data handled by the component can be read.
Integrity
HighData or code can be modified at will.
Availability
NoneAvailability is not affected.

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N. Scored by NVD.

Scoring systemScoreSeverityScored by
CVSS 4.09.3CriticalCNA
CVSS 3.19.1CriticalNVD

Official description

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).

Source: the CVE record as published by its numbering authority, via NVD and CVE.org.

The underlying weakness: Improper Certificate Validation

The product does not validate, or incorrectly validates, a certificate.

How developers prevent this class of flaw

  • Certificates should be carefully managed and checked to assure that data are encrypted with the intended owner's public key.
  • If certificate pinning is being used, ensure that all relevant properties of the certificate are fully validated before the certificate is pinned, including the hostname.

More Improper Certificate Validation vulnerabilities (CWE-295)

Timeline

  1. CVE record published.
  2. CISA published its SSVC assessment (exploitation: none, automatable: yes, technical impact: total).
  3. Record last changed materially (score, affected products, status or references).

References

Other vulnerabilities in BC-JAVA

All BC-JAVA vulnerabilities

Recent Improper Certificate Validation vulnerabilities

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