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TI-2026-40914 Aliases CVE-2026-56741GHSA-2r2c-cx56-8933

JLine: Unauthenticated Remote DoS via Unbounded Telnet NAWS Terminal Geometry

Priority HIGH 72CWE-400Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
None
Attack complexity
Low
Impact type
Denial of service
Confidentiality · integrity · availability
None · None · High
Fix status
Fixed

Attack profile from CVSS 3.1 · CNA. Fix status from CNA and GitHub. Impact type from CWE-400.

Summary

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 apply an upper bound to terminal dimensions received via the Telnet NAWS option, and TelnetIO.handleNAWS() in TelnetIO.java:856-879 reads client-supplied width and height as 16-bit unsigned integers and passes values such as 65535x65535 to setTerminalGeometry(), allowing an unauthenticated remote attacker to repeatedly alternate values and trigger continuous expensive rendering work that causes CPU exhaustion and denial of service. This issue is fixed in versions 3.30.14, 4.0.16, and 4.2.1.

Why it matters now

Exploitation Proof of concept CISA SSVC · not in CISA KEV
EPSS 0.00595 48th percentileScored 2026-11-07
Public exploit Yes 1 exploit referenceTagged by NVD
Fix Fixed jline3 (jline): 3.30.14, 4.0.16, 4.2.1org.jline:jline-remote-telnet (Maven): 4.2.1, 4.0.16, 3.30.14

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
Poc
Automatable
Yes
Technical impact
Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
jlinejline3before 3.30.14; 4.0.0 to before 4.0.16; 4.1.0 to before 4.2.13.30.14, 4.0.16, 4.2.1Patch availableCNA
—org.jline:jline-remote-telnet (Maven)4.1.0 to before 4.2.14.2.1Patch availableGHSA-2r2c-cx56-8933
—org.jline:jline-remote-telnet (Maven)4.0.0 to before 4.0.164.0.16Patch availableGHSA-2r2c-cx56-8933
—org.jline:jline-remote-telnet (Maven)before 3.30.143.30.14Patch availableGHSA-2r2c-cx56-8933
  • jline3 Vendorjline Affected before 3.30.14; 4.0.0 to before 4.0.16; 4.1.0 to before 4.2.1 Fixed in 3.30.14, 4.0.16, 4.2.1 Patch available CNA
  • org.jline:jline-remote-telnet (Maven) Vendor— Affected 4.1.0 to before 4.2.1 Fixed in 4.2.1 Patch available GHSA-2r2c-cx56-8933
  • org.jline:jline-remote-telnet (Maven) Vendor— Affected 4.0.0 to before 4.0.16 Fixed in 4.0.16 Patch available GHSA-2r2c-cx56-8933
  • org.jline:jline-remote-telnet (Maven) Vendor— Affected before 3.30.14 Fixed in 3.30.14 Patch available GHSA-2r2c-cx56-8933

CPE configurations NVD · 1

CPEVersionsRoleVendor
cpe:2.3:a:jline:jline:*:*:*:*:*:*:*:*before 3.30.14; 4.0.0 to before 4.0.16; 4.1.0 to before 4.2.1Vulnerablejline
  • cpe:2.3:a:jline:jline:*:*:*:*:*:*:*:* Versions before 3.30.14; 4.0.0 to before 4.0.16; 4.1.0 to before 4.2.1 Vulnerable ·jline

Remediation

  • Fix · CNA jline3 (jline) Fixed in 3.30.14, 4.0.16, 4.2.1
  • Fix · GHSA-2r2c-cx56-8933 org.jline:jline-remote-telnet (Maven) Fixed in 4.2.1 Advisory →
  • Fix · GHSA-2r2c-cx56-8933 org.jline:jline-remote-telnet (Maven) Fixed in 4.0.16 Advisory →
  • Fix · GHSA-2r2c-cx56-8933 org.jline:jline-remote-telnet (Maven) Fixed in 3.30.14 Advisory →

Vendor assessments

Red Hat

Red Hat rating: Important. Red Hat's page for this CVE →

Not affected: 2 products
  • Red Hat Fuse 7
  • Red Hat OpenShift AI (RHOAI)

Timeline

  1. 2026-10-02 Threatist record created from CVE-2026-56741
  2. 2026-10-03 Alias added: GHSA-2r2c-cx56-8933
  3. 2026-10-13 Affected versions changed · Red Hat
  4. 2026-10-23 EPSS moved to the below the 50th percentile

References

Exploit 1

Patch 3

Advisory 1

Other 4

  • TI-2026-40913 JLine: Unauthenticated Remote Memory Exhaustion via Unbounded Telnet NEW-ENVIRON Variables CVSS 3.1HIGH 7.5
  • TI-2023-27628 An issue in the component GroovyEngine.execute of jline-groovy v3.24.1 allows attackers… CVSS 3.1MEDIUM 5.5

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences