Vulnerability · Published Sep 23, 2026 · Assigned by GitHub_M

CVE-2026-77420JLine: ReDoS via `HISTORY_IGNORE` Configuration Variable

Medium 5.5

In plain English

A medium-severity regular-expression denial of service in jline3 from jline. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.2% (higher than 8% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)5.5Medium

Exploit odds (30 days)0.2%top 92.2% of all CVEs

Exploited in the wildNo reportsCISA SSVC: poc

Attack toolingNoneno public tooling known

Official 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.

Affected packages & fixed versions

Ecosystem	Package	Fixed in	Advisory
Debian:12	jline3	no fix listed	DEBIAN-CVE-2026-77420
Debian:13	jline3	no fix listed	DEBIAN-CVE-2026-77420
Debian:14	jline3	no fix listed	DEBIAN-CVE-2026-77420
Maven	org.jline:jline-reader	4.3.1	GHSA-5q95-hrpc-m3w3
Maven	org.jline:jline-reader	3.30.15	GHSA-5q95-hrpc-m3w3
Ubuntu:22.04:LTS	jline	no fix listed	UBUNTU-CVE-2026-77420
Ubuntu:24.04:LTS	jline	no fix listed	UBUNTU-CVE-2026-77420
Ubuntu:26.04:LTS	jline	no fix listed	UBUNTU-CVE-2026-77420
Ubuntu:26.10	jline	no fix listed	UBUNTU-CVE-2026-77420
Ubuntu:22.04:LTS	jline2	no fix listed	UBUNTU-CVE-2026-77420
Ubuntu:24.04:LTS	jline2	no fix listed	UBUNTU-CVE-2026-77420
Ubuntu:26.04:LTS	jline2	no fix listed	UBUNTU-CVE-2026-77420
Ubuntu:26.10	jline2	no fix listed	UBUNTU-CVE-2026-77420
Ubuntu:22.04:LTS	jline3	no fix listed	UBUNTU-CVE-2026-77420
Ubuntu:24.04:LTS	jline3	no fix listed	UBUNTU-CVE-2026-77420
Ubuntu:26.04:LTS	jline3	no fix listed	UBUNTU-CVE-2026-77420
Ubuntu:26.10	jline3	no fix listed	UBUNTU-CVE-2026-77420

Affected products (as reported)

Vendor	Product	Versions
jline	jline3	>= 3.0.0, < 3.30.15>= 4.0.0, < 4.3.1

Weakness: CWE-1333 · Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

References

https://github.com/jline/jline3/security/advisories/GHSA-5q95-hrpc-m3w3 x_refsource_CONFIRM
https://github.com/jline/jline3/pull/2012 x_refsource_MISC
https://github.com/jline/jline3/pull/2018 x_refsource_MISC
https://github.com/jline/jline3/commit/1d5fc3099e77938b971e197211cad2d4fbb17541 x_refsource_MISC
https://github.com/jline/jline3/commit/341ee69ccc57b7733c1b40d6993219b64b3206ae x_refsource_MISC
https://github.com/jline/jline3/releases/tag/4.3.1 x_refsource_MISC
https://github.com/jline/jline3/releases/tag/jline-3.30.15 x_refsource_MISC