CVE-2026-77422 JLine: ReDoS in Built-in grep Command Amplified by Automatic `.*` Wrapping
Attackers can cause denial of service in JLine applications by submitting crafted regular expressions to the built-in grep command, leading to excessive CPU consumption.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-77422?
CVE-2026-77422 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 grep command in builtins/src/main/java/org/jline/builtins/PosixCommands.java accepts a user-controlled regular expression in grep(...) and, unless line-regexp mode is used, automatically adds a dot-star prefix and suffix before compiling it with Java's backtracking regular expression engine. The wrapping expands the backtracking search space, so a short nested-quantifier expression evaluated against non-matching input can consume excessive CPU and indefinitely block a command worker, including in remotely exposed shell sessions. This issue is fixed in versions 3.30.15 and 4.3.1.
Weakness: CWE-1333
Which versions are affected by CVE-2026-77422?
4 open source packages ship an affected version, including org.jline:jline-builtins.
| Package | Affected | Fixed in |
|---|---|---|
org.jline:jline-builtins Maven | From 3.0.0 | 3.30.15 |
org.jline:jline-builtins Maven | From 3.0.0 | 3.30.15 |
org.jline:jline-builtins Maven | From 4.0.0 | 4.3.1 |
org.jline:jline-builtins Maven | From 4.0.0 | 4.3.1 |
How do I fix CVE-2026-77422?
Upgrade org.jline:jline-builtins to a fixed version for your release line: 3.30.15 or 4.3.1.
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-2026-77422 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-77422 exists.
Sources
Also known as CLEANSTART-2026-AH69997, CLEANSTART-2026-FW62825, CLEANSTART-2026-IC20744, CLEANSTART-2026-LG94890, CLEANSTART-2026-QX36211, CLEANSTART-2026-YI14989 and 21 more.