JLine: ReDoS in Nano Editor Regex Search Mode

Exploitation

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

CVSS

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

EPSS

• CVE-2026-77421: 0.43% estimated exploitation activity in the next 30 days; percentile 37.74 (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 When regex search mode is enabled in the JLine3 nano editor, the user-supplied search term is compiled directly as a Java regular expression with no timeout or backtracking bound. A crafted pattern such as (a+)+b can hang the editor session thread at high CPU, causing a denial of service for that session. Details In builtins/src/main/java/org/jline/builtins/Nano.java, the search implementation uses Pattern.LITERAL only when regex mode is disabled. When regex mode is enabled, the search term is compiled as a raw Java regex: This regex is then applied to buffer content. Because Java's regex engine is backtracking-based, nested-quantifier patterns can take exponential time on non-matching input. Affected source location: - builtins/src/main/java/org/jline/builtins/Nano.java - doSearch(String text) PoC 1. Create a file containing a long run of a characters and open it in the JLine3 nano editor. 2. Enable regex search mode with the editor's regex toggle. 3. Start a search and…

Published by the source

23 Sep 2026, 18:12 UTC

Last modified by the source

23 Sep 2026, 18:27 UTC

Source last checked

26 Oct 2026, 16:55 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-ph9c-7hw9-vhhw

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-ph9c-7hw9-vhhw

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# Patch Next advisory brief: CVE-2026-77421

Advisory: JLine: ReDoS in Nano Editor Regex Search Mode
IDs: CVE-2026-77421, GHSA-ph9c-7hw9-vhhw
Record: https://patchnext.com/advisories/cve-2026-77421 (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 6.5)
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-builtins 4.3.1, 3.30.15. A vendor fix does not mean a deployment is fixed.

## Affected components
- Maven org.jline:jline-builtins: 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-builtins: 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-builtins.
- 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-ph9c-7hw9-vhhw (OSV record GHSA-ph9c-7hw9-vhhw lists affected ranges: Maven org.jline:jline-builtins >=4.0.0 =3.0.0 <3.30.15 (fixed))
- Verified: https://github.com/advisories/GHSA-ph9c-7hw9-vhhw (GitHub-reviewed advisory GHSA-ph9c-7hw9-vhhw lists affected ranges: Maven org.jline:jline-builtins >=4.0.0 =3.0.0 <3.30.15)

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