CVE-2026-56740
JLine: Unauthenticated Remote Memory Exhaustion via Unbounded Telnet NEW-ENVIRON Variables
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.
INFO
Published Date :
July 17, 2026, 10:17 p.m.
Last Modified :
Aug. 18, 2026, 3:23 p.m.
Remotely Exploit :
Yes !
Source :
[email protected]
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS | 134c704f-9b21-4f2e-91b3-4a467353bcc0 | |||||
| CVSS 3.1 | HIGH | [email protected] | ||||
| CVSS 3.1 | HIGH | MITRE-CVE |
Solution
- Update JLine3 to version 3.30.14 or later.
- Update JLine3 to version 4.0.16 or later.
- Update JLine3 to version 4.2.1 or later.
Public PoC/Exploit Available at Github
CVE-2026-56740 has a 1 public
PoC/Exploit available at Github.
Go to the Public Exploits tab to see the list.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-56740.
| URL | Resource |
|---|---|
| https://github.com/jline/jline3/commit/0389f0ee6d0375901b602671ad5dafd4d1d4ee09 | Patch |
| https://github.com/jline/jline3/commit/4ee3a73849ffb9a85ec748e4e8cd8f6d81f84f40 | Patch |
| https://github.com/jline/jline3/commit/934f09e6128cee33c2b13d42b6e859c1ee2d194b | Patch |
| https://github.com/jline/jline3/pull/2000 | Issue Tracking |
| https://github.com/jline/jline3/pull/2001 | Issue Tracking |
| https://github.com/jline/jline3/releases/tag/4.0.16 | Release Notes |
| https://github.com/jline/jline3/releases/tag/4.2.1 | Release Notes |
| https://github.com/jline/jline3/releases/tag/jline-3.30.14 | Release Notes |
| https://github.com/jline/jline3/security/advisories/GHSA-47qp-hqvx-6r3f | Exploit Vendor Advisory |
| https://github.com/jline/jline3/security/advisories/GHSA-47qp-hqvx-6r3f | Exploit Vendor Advisory |
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-56740 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-56740
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
CVEs, conference materials, research.
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-56740 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-56740 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
Initial Analysis by [email protected]
Aug. 18, 2026
Action Type Old Value New Value Added CPE Configuration OR *cpe:2.3:a:jline:jline:*:*:*:*:*:*:*:* versions up to (excluding) 3.30.14 *cpe:2.3:a:jline:jline:*:*:*:*:*:*:*:* versions from (including) 4.0.0 up to (excluding) 4.0.16 *cpe:2.3:a:jline:jline:*:*:*:*:*:*:*:* versions from (including) 4.1.0 up to (excluding) 4.2.1 Added Reference Type GitHub, Inc.: https://github.com/jline/jline3/commit/0389f0ee6d0375901b602671ad5dafd4d1d4ee09 Types: Patch Added Reference Type GitHub, Inc.: https://github.com/jline/jline3/commit/4ee3a73849ffb9a85ec748e4e8cd8f6d81f84f40 Types: Patch Added Reference Type GitHub, Inc.: https://github.com/jline/jline3/commit/934f09e6128cee33c2b13d42b6e859c1ee2d194b Types: Patch Added Reference Type GitHub, Inc.: https://github.com/jline/jline3/pull/2000 Types: Issue Tracking Added Reference Type GitHub, Inc.: https://github.com/jline/jline3/pull/2001 Types: Issue Tracking Added Reference Type GitHub, Inc.: https://github.com/jline/jline3/releases/tag/4.0.16 Types: Release Notes Added Reference Type GitHub, Inc.: https://github.com/jline/jline3/releases/tag/4.2.1 Types: Release Notes Added Reference Type GitHub, Inc.: https://github.com/jline/jline3/releases/tag/jline-3.30.14 Types: Release Notes Added Reference Type GitHub, Inc.: https://github.com/jline/jline3/security/advisories/GHSA-47qp-hqvx-6r3f Types: Exploit, Vendor Advisory Added Reference Type CISA-ADP: https://github.com/jline/jline3/security/advisories/GHSA-47qp-hqvx-6r3f Types: Exploit, Vendor Advisory -
CVE Modified by 134c704f-9b21-4f2e-91b3-4a467353bcc0
Jul. 20, 2026
Action Type Old Value New Value Added Reference https://github.com/jline/jline3/security/advisories/GHSA-47qp-hqvx-6r3f Added SSVC {'id': 'CVE-2026-56740', 'role': 'CISA Coordinator', 'options': [{'exploitation': 'poc'}, {'automatable': 'yes'}, {'technicalImpact': 'partial'}], 'version': '2.0.3', 'timestamp': '2026-07-20T13:57:48.412665Z'} -
New CVE Received by [email protected]
Jul. 17, 2026
Action Type Old Value New Value Added Affected [{'vendor': 'jline', 'product': 'jline3', 'versions': [{'status': 'affected', 'version': '< 3.30.14'}, {'status': 'affected', 'version': '>= 4.0.0, < 4.0.16'}, {'status': 'affected', 'version': '>= 4.1.0, < 4.2.1'}]}] Added 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. Added CVSS V3.1 AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H Added CWE CWE-400 Added Reference https://github.com/jline/jline3/commit/0389f0ee6d0375901b602671ad5dafd4d1d4ee09 Added Reference https://github.com/jline/jline3/commit/4ee3a73849ffb9a85ec748e4e8cd8f6d81f84f40 Added Reference https://github.com/jline/jline3/commit/934f09e6128cee33c2b13d42b6e859c1ee2d194b Added Reference https://github.com/jline/jline3/pull/2000 Added Reference https://github.com/jline/jline3/pull/2001 Added Reference https://github.com/jline/jline3/releases/tag/4.0.16 Added Reference https://github.com/jline/jline3/releases/tag/4.2.1 Added Reference https://github.com/jline/jline3/releases/tag/jline-3.30.14 Added Reference https://github.com/jline/jline3/security/advisories/GHSA-47qp-hqvx-6r3f