JLine is a Java library for handling console input. Prior to 3.30.14, 4.0.16, and 4.2.1, the JLine3 Telnet server remote-telnet module does not limit the number of environment variables a client may inject via the Telnet NEW-ENVIRON option, and TelnetIO.readNEVariables() in TelnetIO.java:1127-1180 stores each variable pair in a HashMap held by ConnectionData, allowing an unauthenticated attacker to flood unique variable pairs before the terminating IAC SE byte and exhaust JVM heap memory with an OutOfMemoryError. This issue is fixed in versions 3.30.14, 4.0.16, and 4.2.1.
History

Tue, 18 Aug 2026 15:30:00 +0000

Type Values Removed Values Added
CPEs cpe:2.3:a:jline:jline:*:*:*:*:*:*:*:*

Tue, 28 Jul 2026 20:45:00 +0000

Type Values Removed Values Added
First Time appeared Jline
Jline jline
Vendors & Products Jline
Jline jline

Mon, 20 Jul 2026 14:30:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'poc', 'Technical Impact': 'partial'}, 'version': '2.0.3'}


Fri, 17 Jul 2026 21:45:00 +0000

Type Values Removed Values Added
Description JLine is a Java library for handling console input. Prior to 3.30.14, 4.0.16, and 4.2.1, the JLine3 Telnet server remote-telnet module does not limit the number of environment variables a client may inject via the Telnet NEW-ENVIRON option, and TelnetIO.readNEVariables() in TelnetIO.java:1127-1180 stores each variable pair in a HashMap held by ConnectionData, allowing an unauthenticated attacker to flood unique variable pairs before the terminating IAC SE byte and exhaust JVM heap memory with an OutOfMemoryError. This issue is fixed in versions 3.30.14, 4.0.16, and 4.2.1.
Title JLine: Unauthenticated Remote Memory Exhaustion via Unbounded Telnet NEW-ENVIRON Variables
Weaknesses CWE-400
References
Metrics cvssV3_1

{'score': 7.5, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H'}


cve-icon MITRE

Status: PUBLISHED

Assigner: GitHub_M

Published: 2026-07-17T21:17:03.239Z

Updated: 2026-07-20T13:58:00.902Z

Reserved: 2026-06-22T19:17:28.959Z

Link: CVE-2026-56740

cve-icon Vulnrichment

Updated: 2026-07-20T13:57:28.578Z

cve-icon NVD

Status : Analyzed

Published: 2026-07-17T22:17:57.153

Modified: 2026-08-18T15:23:04.283

Link: CVE-2026-56740

cve-icon Redhat

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