Bug 2501965 (CVE-2026-56740)

Summary:	CVE-2026-56740 org.jline/jline-remote-telnet: JLine3 Telnet Server: Denial of Service via excessive environment variable injection
Product:	[Other] Security Response	Reporter:	OSIDB Bzimport <bzimport>
Component:	vulnerability	Assignee:	Product Security DevOps Team <prodsec-dev>
Status:	NEW ---	QA Contact:
Severity:	high	Docs Contact:
Priority:	high
Version:	unspecified	CC:	asyoung, gmalinko, janstey, jhollowa, kaycoth, pdelbell, prichard, rstepani, sthirugn
Target Milestone:	---	Keywords:	Security
Target Release:	---
Hardware:	All
OS:	Linux
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Doc Text:	A flaw was found in the JLine3 Telnet server remote-telnet module. An unauthenticated remote attacker can exploit this vulnerability by injecting an excessive number of environment variables through the Telnet NEW-ENVIRON option. This action causes the server to store numerous variable pairs, leading to the exhaustion of Java Virtual Machine (JVM) heap memory and a Denial of Service (DoS) condition.	Story Points:	---
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oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:
Bug Depends On:	2529412
Bug Blocks:

Description OSIDB Bzimport 2026-07-17 22:02:18 UTC

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.