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 apply an upper bound to terminal dimensions received via the Telnet NAWS option, and TelnetIO.handleNAWS() in TelnetIO.java:856-879 reads client-supplied width and height as 16-bit unsigned integers and passes values such as 65535x65535 to setTerminalGeometry(), allowing an unauthenticated remote attacker to repeatedly alternate values and trigger continuous expensive rendering work that causes CPU exhaustion and denial of service. This issue is fixed in versions 3.30.14, 4.0.16, and 4.2.1.

No CVSS v4.0

Attack Vector Network

Attack Complexity Low

Privileges Required None

Scope Unchanged

Confidentiality Impact None

Integrity Impact None

Availability Impact High

User Interaction None

No CVSS v3.0

No CVSS v2

This CVE is not in the KEV list.

The EPSS score is 0.00521.

Exploitation poc

Automatable yes

Technical Impact partial

Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).

Vendor Product Default status Versions
jline jline3 affected
Version Status Constraints
< 3.30.14 affected —
>= 4.0.0, < 4.0.16 affected —
>= 4.1.0, < 4.2.1 affected —

No data.

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Project Subscriptions

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Advisories
Source ID Title
Github GHSA Github GHSA GHSA-2r2c-cx56-8933 JLine3 Telnet server: Unauthenticated Remote DoS via Unbounded Telnet NAWS Terminal Geometry
Fixes

Solution

No solution given by the vendor.

Workaround

No workaround given by the vendor.

References
Link Providers
https://github.com/jline/jline3/commit/3ea9cad8699714dc072fade29d36be0d1e23d708 cve-icon
https://github.com/jline/jline3/commit/733eb353dca7b0ea0252e724445b6defa29c393e cve-icon
https://github.com/jline/jline3/commit/86b7ba7801988aadb1a67555629522a71d603bd3 cve-icon
https://github.com/jline/jline3/pull/2000 cve-icon
https://github.com/jline/jline3/releases/tag/4.0.16 cve-icon
https://github.com/jline/jline3/releases/tag/4.2.1 cve-icon
https://github.com/jline/jline3/security/advisories/GHSA-2r2c-cx56-8933 cve-icon cve-icon
History

Mon, 20 Jul 2026 16:30:00 +0000

Type Values Removed Values Added
Metrics ssvc

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

Fri, 17 Jul 2026 21:30:00 +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 apply an upper bound to terminal dimensions received via the Telnet NAWS option, and TelnetIO.handleNAWS() in TelnetIO.java:856-879 reads client-supplied width and height as 16-bit unsigned integers and passes values such as 65535x65535 to setTerminalGeometry(), allowing an unauthenticated remote attacker to repeatedly alternate values and trigger continuous expensive rendering work that causes CPU exhaustion and denial of service. This issue is fixed in versions 3.30.14, 4.0.16, and 4.2.1.
Title JLine: Unauthenticated Remote DoS via Unbounded Telnet NAWS Terminal Geometry
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'}

Projects

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cve-icon MITRE

Status: PUBLISHED

Assigner: GitHub_M

Published:

Updated: 2026-07-20T15:21:23.382Z

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

Link: CVE-2026-56741

cve-icon Vulnrichment

Updated: 2026-07-20T15:21:18.349Z

cve-icon NVD

No data.

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-07-22T01:45:15Z

Weaknesses