CVE-2026-77422
HighCVSS 7.5Summary
In JLine from 3.0.0 until 3.30.15 and 4.3.1, the built-in grep command accepts a user-controlled regular expression 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.
Risk Assessment
An attacker can cause excessive CPU consumption and indefinitely block a command worker, leading to denial of service, including in remotely exposed shell sessions. This can disrupt availability of JLine-based services.
Recommendation
Upgrade JLine to version 3.30.15 or 4.3.1 (or later) and restrict access to remote shell sessions using JLine.
Other vulnerabilities in JLine
See all- CVE-2026-77423High
In JLine from 3.0.0 until 3.30.15 and 4.3.1, the built-in less viewer passes user-controlled search and display-filter patterns 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.
- CVE-2026-77421Medium
The JLine Java console library has a vulnerability in the built-in nano editor where regex search mode passes a user-controlled term to the regex engine without timeout or backtracking bound. A malicious expression can cause excessive CPU usage and block the editor session thread.
- CVE-2026-77420Medium
The JLine library has a vulnerability in DefaultHistory.matchPatterns where the HISTORY_IGNORE configuration value is converted to a regex with incomplete escaping. An attacker controlling configuration can supply a malicious expression that is reevaluated on each history addition, causing excessive CPU usage and blocking the reader thread.
- CVE-2026-56741High
JLine, a Java library for console input, contains a vulnerability in the Telnet server remote-telnet module. The TelnetIO.handleNAWS() function does not limit terminal dimensions received from the client, allowing an unauthenticated attacker to repeatedly set large values (e.g., 65535x65535), causing intensive rendering calculations and CPU exhaustion (DoS).
- CVE-2026-56740High
JLine is a Java library for console handling. Prior to versions 3.30.14, 4.0.16, and 4.2.1, the Telnet module does not limit the number of environment variables a client can inject. An unauthenticated attacker can send many unique variable pairs, causing JVM heap memory exhaustion and an OutOfMemoryError.
Original NVD description (English source)
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.