JLine: ReDoS via HISTORY_IGNORE Configuration Variable

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

5.5 · CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

EPSS

• CVE-2026-77420: 0.18% estimated exploitation activity in the next 30 days; percentile 7.75 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary The JLine3 HISTORYIGNORE 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 HISTORYIGNORE into a regex: 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 HISTORYIGNORE to a malicious pattern, for example: 2. At the JLine prompt, enter a long non-matching line: 3. Press Enter. Expected result: - The prompt does not…

Published by the source

23 Sep 2026, 18:12 UTC

Last modified by the source

23 Sep 2026, 18:15 UTC

Source last checked

26 Oct 2026, 16:55 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-5q95-hrpc-m3w3

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-5q95-hrpc-m3w3

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# Patch Next advisory brief: CVE-2026-77420

Advisory: JLine: ReDoS via `HISTORY_IGNORE` Configuration Variable
IDs: CVE-2026-77420, GHSA-5q95-hrpc-m3w3
Record: https://patchnext.com/advisories/cve-2026-77420 (revision 2, source checked 26 Oct 2026, 16:55 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 5.5)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: org.jline:jline-reader 4.3.1, 3.30.15. A vendor fix does not mean a deployment is fixed.

## Affected components
- Maven org.jline:jline-reader: affected >= 4.0.0, < 4.3.1; >= 3.0.0, < 3.30.15; fixed in 4.3.1, 3.30.15

## Suggested inspection (read-only)
- Maven org.jline:jline-reader: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on org.jline:jline-reader.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-5q95-hrpc-m3w3 (OSV record GHSA-5q95-hrpc-m3w3 lists affected ranges: Maven org.jline:jline-reader >=4.0.0 =3.0.0 <3.30.15 (fixed))
- Verified: https://github.com/advisories/GHSA-5q95-hrpc-m3w3 (GitHub-reviewed advisory GHSA-5q95-hrpc-m3w3 lists affected ranges: Maven org.jline:jline-reader >=4.0.0 =3.0.0 <3.30.15)

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