Resource exhaustion in jline3 - CVE-2026-56740
Published: September 9, 2026
Vulnerability identifier: #VU148443
CSH Severity: Medium
CVSS v4: 8.7 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-56740
CWE-ID: CWE-400
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote attacker to cause a denial of service.
The vulnerability exists due to uncontrolled resource consumption in the TelnetIO.readNEVariables() environment-variable accumulator when processing Telnet NEW-ENVIRON variable pairs. A remote attacker can send a large number of unique variable pairs to exhaust JVM heap memory.
The issue is reachable during Telnet NEW-ENVIRON negotiation before login.
Affected software
jline3
How to mitigate CVE-2026-56740
Install security update from vendor's website.
jline3 - addressed in versions 3.30.14, 4.2.1