Sign in Sign up
JA · EN · FR
SecPulse
Categories
CVE-2026-56741 high CVSS 7.5

Vulnerability in org.jline:jline-remote-telnet (CVE-2026-56741)

Summary

Vulnerability in org.jline:jline-remote-telnet (CVE-2026-56741). Risk of unauthorized operations or information disclosure. Exploitable via Telnet. Mitigation: upgrade to 3.30.14 or later.

Original description

The description as published by the source.

Summary

The JLine3 Telnet server (remote-telnet module) does not apply an upper bound to
terminal dimensions received via the Telnet NAWS (Negotiate About Window Size) option.
An unauthenticated remote attacker can send a NAWS subnegotiation advertising a
65535×65535 terminal and repeatedly alternate values to trigger continuous, expensive
rendering work on the server, causing CPU exhaustion and denial of service.

Details

TelnetIO.handleNAWS() (TelnetIO.java:856-879) reads the client-supplied width and
height as 16-bit unsigned integers and passes them to setTerminalGeometry():

// TelnetIO.java:869-875
private void setTerminalGeometry(int columns, int rows) {
    if (columns < SMALLEST_BELIEVABLE_WIDTH) columns = DEFAULT_WIDTH;  // lower bound only
    if (rows    < SMALLEST_BELIEVABLE_HEIGHT) rows    = DEFAULT_HEIGHT;
    connectionData.setTerminalGeometry(columns, rows);
    connection.processConnectionEvent(
        new ConnectionEvent(connection, ConnectionEvent.Type.CONNECTION_TERMINAL_GEOMETRY_CHANGED));
}

Only a lower bound is enforced (minimum 20 columns / 6 rows). Values up to 65535 are
accepted and stored. The geometry change event propagates to Telnet.java:153-158 where
it calls:

terminal.setSize(new Size(65535, 65535));
terminal.raise(Signal.WINCH);

The WINCH signal triggers LineReaderImpl.handleSignal() → redisplay(). Inside
redisplay(), multiple paths iterate up to size.getColumns() times:

  • freshLine() (Line…

Source: NIST National Vulnerability Database NVD GitHub Advisory

Auto-generated summary

Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.

A vulnerability tracked as CVE-2026-56741 has been found in org.jline:jline-remote-telnet.
Attackers can target a specific entry point like Telnet over the network to misuse the product.
Risk of unauthorized operations or information disclosure. CVSS score: 7.5/10.
What to do: upgrade org.jline:jline-remote-telnet to 3.30.14 or later.
If unsure, ask your IT team or search "org.jline:jline-remote-telnet CVE-2026-56741" on the vendor's site.

CVE-2026-56741 (org.jline:jline-remote-telnet) — CWE-400 / CVSS v3 7.5
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Attack surface: Telnet
Patched: 3.30.14 — apply immediately
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.

❓ What is the problem

A vulnerability (CWE-400) exists in org.jline:jline-remote-telnet. Attackers reach the vulnerable code path via Telnet without authentication.

📍 Affected scope

Check the vendor advisory for the affected versions of org.jline:jline-remote-telnet. Attack surface: Telnet.

🔥 Severity

Severity: High (CVSS 7.5/10). Risk of unauthorized operations or information disclosure.

🔧 How to fix

Update to 3.30.14.

🛡️ Workaround

Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.

🔍 Detection

Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Audit SBOM/dependencies to find affected services.

Response actions

Concrete steps and command examples for SOC/SRE teams to execute in order

  1. 1
    Identify exposure identify 
    Audit SBOM/dependencies for affected components.

    資産台帳・SBOM・依存マニフェストで org.jline:jline-remote-telnet を使っているサービスとバージョンを洗い出す。

  2. 2
    Apply patch patch 
    Upgrade org.jline:jline-remote-telnet to 3.30.14

    ステージング環境で 3.30.14 に上げて回帰テスト → 本番反映。回帰テストはアプリの主要ハッピーパスを含めること。

  3. 3
    Post-deployment verification verify 
    Confirm patched version is live in production

    パッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。

Affected packages

maven org.jline:jline-remote-telnet
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"3.30.14"}]}]

Fix status by distribution

Fixed packages published by each distribution for this CVE

References

We use cookies for analytics and ad measurement. This setting applies to all Game co., Ltd. sites. Details