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CVE-2026-77421

6.5 · MEDIUM

JLine is a Java library for handling console input.

Published Sep 23, 2026CWE-1333EPSS 0.43%

Overview

CVE-2026-77421 is a medium-severity vulnerability. It was published on September 23, 2026 and has a CVSS 3.1 base score of 6.5 (MEDIUM).

This vulnerability has a CVSS 3.1 base score of 6.5, rated MEDIUM. It can be exploited remotely over the network. Some level of privileges is required for exploitation.

Technical 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.

Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

References

GitHubgithub.com/jline/jline3/commit/1d5fc3099e77938b971e197211cad2d4fbb17541GitHubgithub.com/jline/jline3/commit/341ee69ccc57b7733c1b40d6993219b64b3206aeGitHubgithub.com/jline/jline3/pull/2012GitHubgithub.com/jline/jline3/pull/2018GitHubgithub.com/jline/jline3/releases/tag/4.3.1GitHubgithub.com/jline/jline3/releases/tag/jline-3.30.15GitHubgithub.com/jline/jline3/security/advisories/GHSA-ph9c-7hw9-vhhw

How CyberStrike helps

Frequently asked questions

What is CVE-2026-77421?

CVE-2026-77421 is a medium-severity vulnerability. It was published on September 23, 2026 and has a CVSS 3.1 base score of 6.5 (MEDIUM).

How severe is CVE-2026-77421?

This vulnerability has a CVSS 3.1 base score of 6.5, rated MEDIUM. It can be exploited remotely over the network. Some level of privileges is required for exploitation.

How do I fix or remediate CVE-2026-77421?

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

How can CyberStrike help with CVE-2026-77421?

CyberStrike is an open-source, AI-augmented pentesting engine. Rather than flag a version number, it tests whether an issue like CVE-2026-77421 is actually reachable in your own applications and APIs, then verifies each finding before reporting it. That tells you if the weakness is a real, exploitable risk in your environment or a false positive you can safely deprioritize.

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