CVE-2026-56740: CWE-400: Uncontrolled Resource Consumption in jline jline3
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.
AI Analysis
Technical Summary
CVE-2026-56740 is an uncontrolled resource consumption vulnerability (CWE-400) in the JLine3 Telnet server remote-telnet module. The vulnerability arises because the TelnetIO.readNEVariables() method does not limit the number of environment variables a client can inject via the Telnet NEW-ENVIRON option. Each variable pair is stored in a HashMap within ConnectionData, allowing an unauthenticated attacker to flood the server with unique variable pairs before the terminating IAC SE byte, leading to JVM heap exhaustion and an OutOfMemoryError. This vulnerability affects versions prior to 3.30.14, 4.0.16, and 4.2.1, where it has been fixed.
Potential Impact
An unauthenticated remote attacker can cause a denial of service by exhausting the JVM heap memory of the JLine3 Telnet server through injection of excessive environment variables. This results in an OutOfMemoryError, disrupting service availability. There is no impact on confidentiality or integrity according to the CVSS vector.
Mitigation Recommendations
Upgrade affected JLine3 versions to 3.30.14, 4.0.16, or 4.2.1 or later, where this vulnerability has been fixed. No other mitigation or temporary workaround is indicated in the available data.
CVE-2026-56740: CWE-400: Uncontrolled Resource Consumption in jline jline3
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.
CVSS v3.1
Score 7.5high
Affected software
pkg:maven/org.jline/jline3Run on your own infrastructure? Check whether these packages are installed with threat-finder — our free open-source scanner.
Weaknesses
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
CVE-2026-56740 is an uncontrolled resource consumption vulnerability (CWE-400) in the JLine3 Telnet server remote-telnet module. The vulnerability arises because the TelnetIO.readNEVariables() method does not limit the number of environment variables a client can inject via the Telnet NEW-ENVIRON option. Each variable pair is stored in a HashMap within ConnectionData, allowing an unauthenticated attacker to flood the server with unique variable pairs before the terminating IAC SE byte, leading to JVM heap exhaustion and an OutOfMemoryError. This vulnerability affects versions prior to 3.30.14, 4.0.16, and 4.2.1, where it has been fixed.
Potential Impact
An unauthenticated remote attacker can cause a denial of service by exhausting the JVM heap memory of the JLine3 Telnet server through injection of excessive environment variables. This results in an OutOfMemoryError, disrupting service availability. There is no impact on confidentiality or integrity according to the CVSS vector.
Mitigation Recommendations
Upgrade affected JLine3 versions to 3.30.14, 4.0.16, or 4.2.1 or later, where this vulnerability has been fixed. No other mitigation or temporary workaround is indicated in the available data.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- GitHub_M
- Date Reserved
- 2026-06-22T19:17:28.959Z
- Cvss Version
- 3.1
- State
- PUBLISHED
- Remediation Level
- null
Threat ID: 6a5b401834329bf928c7134a
Added to database: 07/18/2026, 08:58:00 UTC
Last enriched: 07/25/2026, 22:52:51 UTC
Last updated: 09/01/2026, 10:52:09 UTC
Views: 124
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