---
title: "CVE-2026-59639\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-2026-59639?format=md
keywords: index, follow
---

# CVE-2026-59639

Publication date 3 August 2026

Last updated 31 August 2026

---

Ubuntu priority

**Medium**

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

## Cvss 3 Severity Score

**7.5 · High**

[Score breakdown](https://ubuntu.com/security/CVE-2026-59639?format=md#impact-score)

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## Description

In Bouncy Castle for Java before 1.85, CMS verifySignatures returns true
for SignedData with zero signers. This issue also affects Bouncy Castle for
Java LTS before 2.73.12, and Bouncy Castle for Java FIPS (BC-FJA) before
bcpkix-fips 1.0.12 (1.0.X series), 2.0.12 (2.0.X series) and 2.1.12 (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-2026-59639?format=md)
[CVSS v3.0](https://ubuntu.com/security/CVE-2026-59639?format=md)

**Base score**

8.7 · High

* Base metrics

  | Parameter | Value |
  | --- | --- |
  | Attack vector | Network |
  | Attack complexity | Low |
  | Attack requirements | None |
  | Privileges required | None |
  | User interaction | None |
  | Vulnerable system - Confidentiality impact | None |
  | 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 | 8.7 · High |
  | 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:N/VI:H/VA:N/SC:N/SI:N/SA:N/U:Amber

## References

* [MITRE](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2026-59639)
* [NVD](https://nvd.nist.gov/vuln/detail/CVE-2026-59639)
* [Launchpad](https://launchpad.net/bugs/cve/CVE-2026-59639)
* [Debian](https://security-tracker.debian.org/tracker/CVE-2026-59639)

### Other references

* <https://www.cve.org/CVERecord?id=CVE-2026-59639>
* <https://github.com/bcgit/bc-java/wiki/CVE%E2%80%902026%E2%80%9059639>
* <https://github.com/bcgit/bc-java/commit/99ddc6dcc6782e6a76b0dd587c77e62eb7096ad0>