CVE-2026-77423 JLine: ReDoS in Built-in Less Viewer Search
Attackers can cause denial of service in JLine applications by submitting malicious regex patterns to the built-in less viewer, exhausting CPU resources.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-77423?
CVE-2026-77423 is a high-severity denial of service vulnerability in jline3, published on 23 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official 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.
Weakness: CWE-1333
Which versions are affected by CVE-2026-77423?
How do I fix CVE-2026-77423?
No fix has been published for CVE-2026-77423 yet. Limit exposure of the affected software until one is available.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-77423 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-77423 exists.
Sources
Also known as DEBIAN-CVE-2026-77423, GHSA-2v9w-34q6-wpqx, UBUNTU-CVE-2026-77423.