JLine: Unauthenticated Remote Memory Exhaustion via Unbounded Telnet NEW-ENVIRON Variables

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Summary

CVECVE-2026-56740
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-07-17 22:17:57 UTC
Updated2026-07-20 15:16:44 UTC
DescriptionJLine 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.

Risk And Classification

Primary CVSS: v3.1 7.5 HIGH from [email protected]

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS: 0.005110000 probability, percentile 0.402500000 (date 2026-07-20)

Problem Types: CWE-400 | CWE-400 CWE-400: Uncontrolled Resource Consumption

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary7.5HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
3.1CNADECLARED7.5HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Jline Jline3 affected < 3.30.14 Not specified
CNA Jline Jline3 affected >= 4.0.0, < 4.0.16 Not specified
CNA Jline Jline3 affected >= 4.1.0, < 4.2.1 Not specified

References

ReferenceSourceLinkTags
github.com/jline/jline3/security/advisories/GHSA-47qp-hqvx-6r3f 134c704f-9b21-4f2e-91b3-4a467353bcc0 github.com
github.com/jline/jline3/pull/2000 [email protected] github.com
github.com/jline/jline3/commit/0389f0ee6d0375901b602671ad5dafd4d1d4ee09 [email protected] github.com
github.com/jline/jline3/releases/tag/4.0.16 [email protected] github.com
github.com/jline/jline3/releases/tag/jline-3.30.14 [email protected] github.com
github.com/jline/jline3/commit/4ee3a73849ffb9a85ec748e4e8cd8f6d81f84f40 [email protected] github.com
github.com/jline/jline3/pull/2001 [email protected] github.com
github.com/jline/jline3/releases/tag/4.2.1 [email protected] github.com
github.com/jline/jline3/commit/934f09e6128cee33c2b13d42b6e859c1ee2d194b [email protected] github.com
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