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CVE-2026-56740

7.5 · HIGH

JLine is a Java library for handling console input.

Published Jul 17, 2026CWE-400EPSS 0.88%

Overview

CVE-2026-56740 is a high-severity vulnerability. It was published on July 17, 2026 and has a CVSS 3.1 base score of 7.5 (HIGH).

This vulnerability has a CVSS 3.1 base score of 7.5, rated HIGH. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.

Technical 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.

Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

References

GitHubgithub.com/jline/jline3/commit/0389f0ee6d0375901b602671ad5dafd4d1d4ee09GitHubgithub.com/jline/jline3/commit/4ee3a73849ffb9a85ec748e4e8cd8f6d81f84f40GitHubgithub.com/jline/jline3/commit/934f09e6128cee33c2b13d42b6e859c1ee2d194bGitHubgithub.com/jline/jline3/pull/2000GitHubgithub.com/jline/jline3/pull/2001GitHubgithub.com/jline/jline3/releases/tag/4.0.16GitHubgithub.com/jline/jline3/releases/tag/4.2.1GitHubgithub.com/jline/jline3/releases/tag/jline-3.30.14GitHubgithub.com/jline/jline3/security/advisories/GHSA-47qp-hqvx-6r3fGitHubgithub.com/jline/jline3/security/advisories/GHSA-47qp-hqvx-6r3f

How CyberStrike helps

Frequently asked questions

What is CVE-2026-56740?

CVE-2026-56740 is a high-severity vulnerability. It was published on July 17, 2026 and has a CVSS 3.1 base score of 7.5 (HIGH).

How severe is CVE-2026-56740?

This vulnerability has a CVSS 3.1 base score of 7.5, rated HIGH. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.

How do I fix or remediate CVE-2026-56740?

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

How can CyberStrike help with CVE-2026-56740?

CyberStrike is an open-source, AI-augmented pentesting engine. Rather than flag a version number, it tests whether an issue like CVE-2026-56740 is actually reachable in your own applications and APIs, then verifies each finding before reporting it. That tells you if the weakness is a real, exploitable risk in your environment or a false positive you can safely deprioritize.

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