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Vulnerability · Published Jul 17, 2026 · Assigned by GitHub_M

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

High 7.5

In plain English

A high-severity uncontrolled resource consumption in jline3 from jline. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.6% (higher than 48% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)7.5High
Exploit odds (30 days)0.6%top 51.5% of all CVEs
Exploited in the wildNo reportsCISA SSVC: poc
Attack toolingNoneno public tooling known

Official 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.

Affected packages & fixed versions

EcosystemPackageFixed inAdvisory
Debian:12jlineno fix listedDEBIAN-CVE-2026-56740
Debian:13jlineno fix listedDEBIAN-CVE-2026-56740
Debian:14jlineno fix listedDEBIAN-CVE-2026-56740
Debian:12jline2no fix listedDEBIAN-CVE-2026-56740
Debian:13jline2no fix listedDEBIAN-CVE-2026-56740
Debian:14jline2no fix listedDEBIAN-CVE-2026-56740
Debian:12jline3no fix listedDEBIAN-CVE-2026-56740
Debian:13jline3no fix listedDEBIAN-CVE-2026-56740
Debian:14jline3no fix listedDEBIAN-CVE-2026-56740
Mavenorg.jline:jline-remote-telnet4.2.1GHSA-47qp-hqvx-6r3f
Mavenorg.jline:jline-remote-telnet4.0.16GHSA-47qp-hqvx-6r3f
Mavenorg.jline:jline-remote-telnet3.30.14GHSA-47qp-hqvx-6r3f
Ubuntu:22.04:LTSjlineno fix listedUBUNTU-CVE-2026-56740
Ubuntu:24.04:LTSjlineno fix listedUBUNTU-CVE-2026-56740
Ubuntu:26.04:LTSjlineno fix listedUBUNTU-CVE-2026-56740
Ubuntu:26.10jlineno fix listedUBUNTU-CVE-2026-56740
Ubuntu:22.04:LTSjline2no fix listedUBUNTU-CVE-2026-56740
Ubuntu:24.04:LTSjline2no fix listedUBUNTU-CVE-2026-56740
Ubuntu:26.04:LTSjline2no fix listedUBUNTU-CVE-2026-56740
Ubuntu:26.10jline2no fix listedUBUNTU-CVE-2026-56740
Ubuntu:22.04:LTSjline3no fix listedUBUNTU-CVE-2026-56740
Ubuntu:24.04:LTSjline3no fix listedUBUNTU-CVE-2026-56740
Ubuntu:26.04:LTSjline3no fix listedUBUNTU-CVE-2026-56740
Ubuntu:26.10jline3no fix listedUBUNTU-CVE-2026-56740

Affected products (as reported)

VendorProductVersions
jline jline3 < 3.30.14>= 4.0.0, < 4.0.16>= 4.1.0, < 4.2.1

Weakness: CWE-400 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

References