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.
CVSS Score
HIGH
Affected Products
| Vendor | Product | Versions |
|---|---|---|
| Jline | Jline | < 3.30.14 |
Related Weaknesses (CWE)
References
- https://github.com/jline/jline3/commit/0389f0ee6d0375901b602671ad5dafd4d1d4ee09Patch
- https://github.com/jline/jline3/commit/4ee3a73849ffb9a85ec748e4e8cd8f6d81f84f40Patch
- https://github.com/jline/jline3/commit/934f09e6128cee33c2b13d42b6e859c1ee2d194bPatch
- https://github.com/jline/jline3/pull/2000Issue Tracking
- https://github.com/jline/jline3/pull/2001Issue Tracking
- https://github.com/jline/jline3/releases/tag/4.0.16Release Notes
- https://github.com/jline/jline3/releases/tag/4.2.1Release Notes
- https://github.com/jline/jline3/releases/tag/jline-3.30.14Release Notes
- https://github.com/jline/jline3/security/advisories/GHSA-47qp-hqvx-6r3fExploitVendor Advisory
- https://github.com/jline/jline3/security/advisories/GHSA-47qp-hqvx-6r3fExploitVendor Advisory
FAQ
What is CVE-2026-56740?
CVE-2026-56740 is a vulnerability with a CVSS score of 7.5 (HIGH). 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 i...
How severe is CVE-2026-56740?
CVE-2026-56740 has been rated HIGH with a CVSS base score of 7.5/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2026-56740?
Check the references section above for vendor advisories and patch information. Affected products include: Jline Jline.