---
title: "CVE-2026-77421\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-2026-77421?format=md
keywords: index, follow
---

# CVE-2026-77421

Publication date 24 September 2026

Last updated 24 September 2026

---

Ubuntu priority

**Medium**

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

## Cvss 3 Severity Score

**6.5 · Medium**

[Score breakdown](https://ubuntu.com/security/CVE-2026-77421?format=md#impact-score)

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## Description

JLine is a Java library for handling console input. From 3.0.0 until
3.30.15 and 4.3.1, the JLine built-in nano editor's regex search mode
passes a user-controlled search term from doSearch(String text) in
builtins/src/main/java/org/jline/builtins/Nano.java to Java's backtracking
regular expression engine without a timeout or backtracking bound. A
nested-quantifier expression evaluated against non-matching buffer content
can consume excessive CPU and indefinitely block the editor session thread,
and remote multi-user deployments can lose a worker thread for each
affected session. This issue is fixed in versions 3.30.15 and 4.3.1.

## Status

Show unmaintained releases

| Package | Ubuntu Release | Status |
| --- | --- | --- |
| jline | 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 |
| 14.04 LTS trusty | Needs evaluation |
| jline2 | 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 |
| 14.04 LTS trusty | Needs evaluation |
| jline3 | 26.04 LTS resolute | Needs evaluation |
| 24.04 LTS noble | Needs evaluation |
| 22.04 LTS jammy | 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**

6.5 · Medium

* Base metrics

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

  | Parameter | Value |
  | --- | --- |
  | Base score | 6.5 · Medium |
  | Exploitability score | - |
  | Impact score | - |

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

## References

* [MITRE](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2026-77421)
* [NVD](https://nvd.nist.gov/vuln/detail/CVE-2026-77421)
* [Launchpad](https://launchpad.net/bugs/cve/CVE-2026-77421)
* [Debian](https://security-tracker.debian.org/tracker/CVE-2026-77421)

### Other references

* <https://www.cve.org/CVERecord?id=CVE-2026-77421>
* <https://github.com/jline/jline3/security/advisories/GHSA-ph9c-7hw9-vhhw>
* <https://github.com/jline/jline3/pull/2018>
* <https://github.com/jline/jline3/commit/341ee69ccc57b7733c1b40d6993219b64b3206ae>
* <https://github.com/jline/jline3/commit/1d5fc3099e77938b971e197211cad2d4fbb17541>
* <https://github.com/jline/jline3/pull/2012>
* <https://github.com/jline/jline3/releases/tag/4.3.1>
* <https://github.com/jline/jline3/releases/tag/jline-3.30.15>