Vulnerability in Jline Jline3
CVE-2026-77420
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.
Vulnerability class: ReDoS (Regular Expression Denial of Service)
Published .
CVSS v3 metric
CVSS v3 base score 5.5 (Medium). Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H.
EPSS exploit prediction
No EPSS score from FIRST.org yet. New CVEs usually get one within a few days; no score means no signal yet, not low risk. How EPSS works.
Affected products
- Jline Jline3 — versions >= 3.0.0, < 3.30.15, >= 4.0.0, < 4.3.1
Weakness classification (CWE)
References
- github.com/jline/jline3/security/advisories/GHSA-5q95-hrpc-m3w3
- github.com/jline/jline3/pull/2012
- github.com/jline/jline3/pull/2018
- github.com/jline/jline3/commit/1d5fc3099e77938b971e197211cad2d4fbb17541
- github.com/jline/jline3/commit/341ee69ccc57b7733c1b40d6993219b64b3206ae
- github.com/jline/jline3/releases/tag/4.3.1
- github.com/jline/jline3/releases/tag/jline-3.30.15
Frequently asked questions
- What is CVE-2026-77420?
- CVE-2026-77420 is a medium-severity vulnerability in Jline Jline3, classified under Inefficient Regular Expression Complexity. CVSS score: 5.5/10. Published 2026-09-23.
- How severe is CVE-2026-77420?
- Medium severity. CVSS v3 base score is 5.5 out of 10.