---
title: "CVE-2026-16615\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-2026-16615?format=md
keywords: index, follow
---

# CVE-2026-16615

Publication date 22 July 2026

Last updated 6 August 2026

---

Ubuntu priority

**Medium**

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

## Cvss 3 Severity Score

**6.8 · Medium**

[Score breakdown](https://ubuntu.com/security/CVE-2026-16615?format=md#impact-score)

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## Description

A flaw was found in librest. The PKCE implementation for OAuth
authorization uses the GRand function from the GLib API, a
cryptographically insecure pseudo-random number generator. Because the
generated "code verifier" lacks sufficient cryptographic entropy, a
malicious actor can reverse-engineer the pseudo-random number generator
(PRNG) seed to predict or reconstruct the code verifier string, allowing an
attacker to bypass PKCE protections and successfully impersonate the client
during the OAuth 2.0 authorization flow.

## Status

Show unmaintained releases

| Package | Ubuntu Release | Status |
| --- | --- | --- |
| librest | 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 v3.0

**Base score**

6.8 · Medium

* Base metrics

  | Parameter | Value |
  | --- | --- |
  | Attack vector | Network |
  | Attack complexity | High |
  | Privileges required | None |
  | User interaction | Required |
  | Scope | Unchanged |
  | Confidentiality impact | High |
  | Integrity impact | High |
  | Availability impact | None |
* Scores

  | Parameter | Value |
  | --- | --- |
  | Base score | 6.8 · Medium |
  | Exploitability score | - |
  | Impact score | - |

**Vector:** CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:N

## References

* [MITRE](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2026-16615)
* [NVD](https://nvd.nist.gov/vuln/detail/CVE-2026-16615)
* [Launchpad](https://launchpad.net/bugs/cve/CVE-2026-16615)
* [Debian](https://security-tracker.debian.org/tracker/CVE-2026-16615)

### Other references

* <https://www.cve.org/CVERecord?id=CVE-2026-16615>