CVE-2026-56741
JLine: Unauthenticated Remote DoS via Unbounded Telnet NAWS Terminal Geometry
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.
INFO
Published Date :
July 17, 2026, 10:17 p.m.
Last Modified :
Oct. 24, 2026, 8:10 p.m.
Remotely Exploit :
Yes !
Source :
[email protected]
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS | 134c704f-9b21-4f2e-91b3-4a467353bcc0 | |||||
| CVSS 3.1 | HIGH | [email protected] | ||||
| CVSS 3.1 | HIGH | MITRE-CVE |
Solution
- Update JLine to version 3.30.14 or later.
- Update JLine to version 4.0.16 or later.
- Update JLine to version 4.2.1 or later.
Public PoC/Exploit Available at Github
CVE-2026-56741 has a 1 public
PoC/Exploit available at Github.
Go to the Public Exploits tab to see the list.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-56741.
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-56741 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-56741
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
CVEs, conference materials, research.
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-56741 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-56741 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
CVE Translated by [email protected]
Oct. 24, 2026
Action Type Old Value New Value Added Translation Title: jline3 de jline, Description: JLine es una biblioteca Java para manejar la entrada de consola. Antes de las versiones 3.30.14, 4.0.16 y 4.2.1, el módulo remote-telnet del servidor Telnet de JLine3 no aplica un límite superior a las dimensiones del terminal recibidas a través de la opción Telnet NAWS, y TelnetIO.handleNAWS() en TelnetIO.java:856-879 lee el ancho y alto proporcionados por el cliente como enteros sin signo de 16 bits y pasa valores como 65535x65535 a setTerminalGeometry(), permitiendo a un atacante remoto no autenticado alternar repetidamente los valores y desencadenar un trabajo de renderizado costoso y continuo que causa el agotamiento de la CPU y la denegación de servicio. Este problema se ha solucionado en las versiones 3.30.14, 4.0.16 y 4.2.1. -
Initial Analysis by [email protected]
Aug. 18, 2026
Action Type Old Value New Value Added CPE Configuration OR *cpe:2.3:a:jline:jline:*:*:*:*:*:*:*:* versions up to (excluding) 3.30.14 *cpe:2.3:a:jline:jline:*:*:*:*:*:*:*:* versions from (including) 4.0.0 up to (excluding) 4.0.16 *cpe:2.3:a:jline:jline:*:*:*:*:*:*:*:* versions from (including) 4.1.0 up to (excluding) 4.2.1 Added Reference Type GitHub, Inc.: https://github.com/jline/jline3/commit/3ea9cad8699714dc072fade29d36be0d1e23d708 Types: Patch Added Reference Type GitHub, Inc.: https://github.com/jline/jline3/commit/733eb353dca7b0ea0252e724445b6defa29c393e Types: Patch Added Reference Type GitHub, Inc.: https://github.com/jline/jline3/commit/86b7ba7801988aadb1a67555629522a71d603bd3 Types: Patch Added Reference Type GitHub, Inc.: https://github.com/jline/jline3/pull/2000 Types: Issue Tracking Added Reference Type GitHub, Inc.: https://github.com/jline/jline3/releases/tag/4.0.16 Types: Release Notes Added Reference Type GitHub, Inc.: https://github.com/jline/jline3/releases/tag/4.2.1 Types: Release Notes Added Reference Type GitHub, Inc.: https://github.com/jline/jline3/security/advisories/GHSA-2r2c-cx56-8933 Types: Exploit, Vendor Advisory Added Reference Type CISA-ADP: https://github.com/jline/jline3/security/advisories/GHSA-2r2c-cx56-8933 Types: Exploit, Vendor Advisory -
CVE Modified by 134c704f-9b21-4f2e-91b3-4a467353bcc0
Jul. 20, 2026
Action Type Old Value New Value Added Reference https://github.com/jline/jline3/security/advisories/GHSA-2r2c-cx56-8933 Added SSVC {'id': 'CVE-2026-56741', 'role': 'CISA Coordinator', 'options': [{'exploitation': 'poc'}, {'automatable': 'yes'}, {'technicalImpact': 'partial'}], 'version': '2.0.3', 'timestamp': '2026-07-20T15:21:00.621662Z'} -
New CVE Received by [email protected]
Jul. 17, 2026
Action Type Old Value New Value Added Affected [{'vendor': 'jline', 'product': 'jline3', 'versions': [{'status': 'affected', 'version': '< 3.30.14'}, {'status': 'affected', 'version': '>= 4.0.0, < 4.0.16'}, {'status': 'affected', 'version': '>= 4.1.0, < 4.2.1'}]}] 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. Added CVSS V3.1 AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H Added CWE CWE-400 Added Reference https://github.com/jline/jline3/commit/3ea9cad8699714dc072fade29d36be0d1e23d708 Added Reference https://github.com/jline/jline3/commit/733eb353dca7b0ea0252e724445b6defa29c393e Added Reference https://github.com/jline/jline3/commit/86b7ba7801988aadb1a67555629522a71d603bd3 Added Reference https://github.com/jline/jline3/pull/2000 Added Reference https://github.com/jline/jline3/releases/tag/4.0.16 Added Reference https://github.com/jline/jline3/releases/tag/4.2.1 Added Reference https://github.com/jline/jline3/security/advisories/GHSA-2r2c-cx56-8933