---
title: "CVE-2026-8763\n    | Ubuntu"
description: Ubuntu is an open source software operating system that runs from the
  desktop, to the cloud, to all your internet connected things.
url: https://ubuntu.com/security/CVE-2026-8763?format=md
keywords: index, follow
---

# CVE-2026-8763

Publication date 3 August 2026

Last updated 4 September 2026

---

Ubuntu priority

**Medium**

[Why this priority?](https://ubuntu.com/security/cves/about#priority )

## Cvss 3 Severity Score

**9.1 · Critical**

[Score breakdown](https://ubuntu.com/security/CVE-2026-8763?format=md#impact-score)

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## 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).

## Status

Show unmaintained releases

| Package | Ubuntu Release | Status |
| --- | --- | --- |
| bouncycastle | 26.04 LTS resolute | Needs evaluation |
| 24.04 LTS noble | Needs evaluation |
| 22.04 LTS jammy | Needs evaluation |
| 20.04 LTS focal | Needs evaluation |
| 18.04 LTS bionic | Needs evaluation |
| 16.04 LTS xenial | Needs evaluation |

---

* [How can I get the fixes?](https://ubuntu.com/security/cves/about#security)
* [What do statuses mean?](https://ubuntu.com/security/cves/about#statuses)

## Severity score breakdown

CVSS version:

CVSS v4.0

[CVSS v4.0](https://ubuntu.com/security/CVE-2026-8763?format=md)
[CVSS v3.0](https://ubuntu.com/security/CVE-2026-8763?format=md)

**Base score**

9.3 · Critical

* Base metrics

  | Parameter | Value |
  | --- | --- |
  | Attack vector | Network |
  | Attack complexity | Low |
  | Attack requirements | None |
  | Privileges required | None |
  | User interaction | None |
  | Vulnerable system - Confidentiality impact | High |
  | Vulnerable system - Integrity impact | High |
  | Vulnerable system - Availability impact | None |
  | Subsequent system - Confidentiality impact | None |
  | Subsequent system - Integrity impact | None |
  | Subsequent system - Availability impact | None |
* Scores

  | Parameter | Value |
  | --- | --- |
  | Base score | 9.3 · Critical |
  | Base + Threat score | - |
  | Base + Environmental score | - |
  | Base + Threat + Environmental score | - |

**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

## References

* [MITRE](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2026-8763)
* [NVD](https://nvd.nist.gov/vuln/detail/CVE-2026-8763)
* [Launchpad](https://launchpad.net/bugs/cve/CVE-2026-8763)
* [Debian](https://security-tracker.debian.org/tracker/CVE-2026-8763)

### Other references

* <https://www.cve.org/CVERecord?id=CVE-2026-8763>
* <https://github.com/bcgit/bc-java/wiki/CVE%E2%80%902026%E2%80%908763>
* <https://github.com/bcgit/bc-java/commit/2c28b253a44681fbbc562561eab6ad383d2ae558>