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CVE-2026-56740— JLine: Unauthenticated Remote Memory Exhaustion via Unbounded Telnet NEW-ENVIRON Variables

Quick assessment

Affected
jline jline3
Exploitation
Public or AI PoC available; prioritize validation
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

JLine是JLine组织开源的一个用于处理控制台输入的 Java 库。 JLine 3.30.14之前版本、4.0.0版本至4.0.16之前版本和4.1.0版本至4.2.1之前版本存在资源管理错误漏洞，该漏洞源于JLine3 Telnet服务器远程telnet模块未限制客户端通过Telnet NEW-ENVIRON选项注入的环境变量数量，TelnetIO.readNEVariables()函数将每个变量对存储在ConnectionData持有的HashMap中，可能导致未经身份验证的攻击者在终止IAC

CVSS 7.5 · High EPSS 0.88% · P58

Possible ATT&CK Techniques 1 AI

T1496 · Resource Hijacking

Affected Version Matrix 3

VendorProduct Version RangeStatus
jline jline3 < 3.30.14 affected
>= 4.0.0, < 4.0.16 affected
>= 4.1.0, < 4.2.1 affected
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I. Basic Information for CVE-2026-56740

Vulnerability Information
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Vulnerability Title
JLine: Unauthenticated Remote Memory Exhaustion via Unbounded Telnet NEW-ENVIRON Variables
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
未加控制的资源消耗(资源穷尽)
Source: CVE Program / CVE List V5
Vulnerability Title
JLine 资源管理错误漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
JLine是JLine组织开源的一个用于处理控制台输入的 Java 库。 JLine 3.30.14之前版本、4.0.0版本至4.0.16之前版本和4.1.0版本至4.2.1之前版本存在资源管理错误漏洞，该漏洞源于JLine3 Telnet服务器远程telnet模块未限制客户端通过Telnet NEW-ENVIRON选项注入的环境变量数量，TelnetIO.readNEVariables()函数将每个变量对存储在ConnectionData持有的HashMap中，可能导致未经身份验证的攻击者在终止IAC
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
jline jline3 < 3.30.14 -

II. Public POCs for CVE-2026-56740

# POC Description Source Link Shenlong Link
AI-Generated POC Premium
Qwen3.6-35B-A3B · 8062 chars
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III. Intelligence Information for CVE-2026-56740

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Patches & Fixes for CVE-2026-56740 (5)

Vendor Advisories for CVE-2026-56740 (1)

Vendor Pages for CVE-2026-56740 (3)

IV. Related Vulnerabilities

Same product: jline3
Same vendor: jline
Same weakness: CWE-400

V. Comments for CVE-2026-56740

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