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CVE-2026-77420 medium CVSS 5.5

Vulnerability in org.jline:jline-reader (CVE-2026-77420)

Summary

Vulnerability in org.jline:jline-reader (CVE-2026-77420). Risk of unauthorized operations or information disclosure. Exploitable via HISTORY_IGNORE. Mitigation: upgrade to 3.30.15 or later.

Original description

The description as published by the source.

Summary

The JLine3 HISTORY_IGNORE variable is converted into a Java regular expression with
only partial escaping. As a result, regex metacharacters other than * and : are
passed through to the regex engine. A crafted value such as (a+)+b can cause
catastrophic backtracking each time a command line is added to history, hanging the
reader thread at high CPU.

Details

In reader/src/main/java/org/jline/reader/impl/history/DefaultHistory.java,
matchPatterns() converts HISTORY_IGNORE into a regex:

for (int i = 0; i < patterns.length(); i++) {
    char ch = patterns.charAt(i);
    if (ch == '\\') {
        ch = patterns.charAt(++i);
        sb.append(ch);
    } else if (ch == ':') {
        sb.append('|');
    } else if (ch == '*') {
        sb.append('.').append('*');
    } else {
        sb.append(ch);
    }
}
return line.matches(sb.toString());

This logic translates wildcard syntax but does not escape regex metacharacters such as
(, ), +, ?, {, }, [, and ]. Those characters therefore reach the Java
regex engine unchanged.

Affected source location:

  • reader/src/main/java/org/jline/reader/impl/history/DefaultHistory.java
  • matchPatterns(String patterns, String line)

PoC

  1. Configure HISTORY_IGNORE to a malicious pattern, for example:
set history-ignore "(a+)+b"
  1. At the JLine prompt, enter a long non-matching line:
aaaaaaaaaaaaaaaaaaaaaaaaaaax
  1. Press Enter.

Expected result:

  • The promp…

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-2026-77420 has been found in org.jline:jline-reader.
Attackers can target a specific entry point like HISTORY_IGNORE over the network to misuse the product.
Risk of unauthorized operations or information disclosure. CVSS score: 5.5/10.
What to do: upgrade org.jline:jline-reader to 3.30.15 or later.
If unsure, ask your IT team or search "org.jline:jline-reader CVE-2026-77420" on the vendor's site.

CVE-2026-77420 (org.jline:jline-reader) — CWE-1333 / CVSS v3 5.5
Attack vector: local / no user interaction
Attack surface: HISTORY_IGNORE
Patched: 3.30.15 — 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-1333) exists in org.jline:jline-reader. Attackers reach the vulnerable code path via HISTORY_IGNORE.

📍 Affected scope

Check the vendor advisory for the affected versions of org.jline:jline-reader. Attack surface: HISTORY_IGNORE.

🔥 Severity

Severity: Medium (CVSS 5.5/10). Risk of unauthorized operations or information disclosure.

🔧 How to fix

Update to 3.30.15.

🛡️ 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-reader 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-reader to 3.30.15

    ステージング環境で 3.30.15 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-reader
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"3.30.15"}]}]

Fix status by distribution

Fixed packages published by each distribution for this CVE

References

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