Vulnerability-Lookup

CVE-2026-77421 (GCVE-0-2026-77421)

Vulnerability from cvelistv5 – Published: 2026-09-23 18:07 – Updated: 2026-09-23 19:43

Title

JLine: ReDoS in Nano Editor Regex Search Mode

Summary

JLine is a Java library for handling console input. From 3.0.0 until 3.30.15 and 4.3.1, the JLine built-in nano editor's regex search mode passes a user-controlled search term from doSearch(String text) in builtins/src/main/java/org/jline/builtins/Nano.java to Java's backtracking regular expression engine without a timeout or backtracking bound. A nested-quantifier expression evaluated against non-matching buffer content can consume excessive CPU and indefinitely block the editor session thread, and remote multi-user deployments can lose a worker thread for each affected session. This issue is fixed in versions 3.30.15 and 4.3.1.

Severity

6.5 (Medium)


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

SSVC

Exploitation: none Automatable: no Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-09-23 19:05 UTC

CWE

CWE-1333 - Inefficient Regular Expression Complexity

Assigner

GitHub_M mitre root

References

7 references

URL	Tags
https://github.com/jline/jline3/security/advisori…	x_refsource_CONFIRM
https://github.com/jline/jline3/pull/2012	x_refsource_MISC
https://github.com/jline/jline3/pull/2018	x_refsource_MISC
https://github.com/jline/jline3/commit/1d5fc3099e…	x_refsource_MISC
https://github.com/jline/jline3/commit/341ee69ccc…	x_refsource_MISC
https://github.com/jline/jline3/releases/tag/4.3.1	x_refsource_MISC
https://github.com/jline/jline3/releases/tag/jlin…	x_refsource_MISC

Impacted products

1 product

Vendor	Product	Version	CPE status
jline	jline3	Affected: >= 3.0.0, < 3.30.15 Affected: >= 4.0.0, < 4.3.1	guessed

Show details on NVD website

JSON

To clipboard

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FKIE_CVE-2026-77421

Vulnerability from fkie_nvd - Published: 2026-09-23 19:19 - Updated: 2026-09-23 20:17

Severity

6.5 (Medium) - CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Summary

References

	URL	Tags
	security-advisories@github.com	https://github.com/jline/jline3/commit/1d5fc3099e77938b971e197211cad2d4fbb17541
	security-advisories@github.com	https://github.com/jline/jline3/commit/341ee69ccc57b7733c1b40d6993219b64b3206ae
	security-advisories@github.com	https://github.com/jline/jline3/pull/2012
	security-advisories@github.com	https://github.com/jline/jline3/pull/2018
	security-advisories@github.com	https://github.com/jline/jline3/releases/tag/4.3.1
	security-advisories@github.com	https://github.com/jline/jline3/releases/tag/jline-3.30.15
	security-advisories@github.com	https://github.com/jline/jline3/security/advisories/GHSA-ph9c-7hw9-vhhw

Impacted products

	Vendor	Product	Version

JSON

To clipboard

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      "source": "security-advisories@github.com",
      "url": "https://github.com/jline/jline3/releases/tag/jline-3.30.15"
    },
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/jline/jline3/security/advisories/GHSA-ph9c-7hw9-vhhw"
    }
  ],
  "sourceIdentifier": "security-advisories@github.com",
  "vulnStatus": "Received",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-1333"
        }
      ],
      "source": "security-advisories@github.com",
      "type": "Secondary"
    }
  ]
}

GHSA-PH9C-7HW9-VHHW

Vulnerability from github – Published: 2026-09-23 18:12 – Updated: 2026-09-23 18:12

Summary

JLine: ReDoS in Nano Editor Regex Search Mode

Details

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:

Pattern pat = Pattern.compile(
        searchTerm,
        (searchCaseSensitive ? 0 : Pattern.CASE_INSENSITIVE | Pattern.UNICODE_CASE)
                | (searchRegexp ? 0 : Pattern.LITERAL));

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

Create a file containing a long run of a characters and open it in the JLine3 nano editor.
Enable regex search mode with the editor's regex toggle.
Start a search and enter the pattern (a+)+b.

Expected result: - The editor stops responding. - The session thread consumes high CPU.

Reproduction environment: - JLine3 on x86_64 Linux - OpenJDK 25.0.2

Impact

This is a denial-of-service vulnerability caused by catastrophic regex backtracking. Applications embedding org.jline:jline-builtins and exposing the nano editor are impacted. In local use, the user can hang their own session. In remote multi-user deployments, an attacker can occupy a server worker thread indefinitely.

Suggested Fix

The preferred fix for the current git head is to use a linear-time regex engine for regex search mode while preserving literal matching behavior when regex mode is off.

Suggested patch:

diff --git a/builtins/pom.xml b/builtins/pom.xml
--- a/builtins/pom.xml
+++ b/builtins/pom.xml
@@
         <dependency>
+            <groupId>com.google.re2j</groupId>
+            <artifactId>re2j</artifactId>
+            <version>1.8</version>
+        </dependency>
+        <dependency>
             <groupId>org.jline</groupId>
             <artifactId>jline-reader</artifactId>
         </dependency>

diff --git a/builtins/src/main/java/org/jline/builtins/Nano.java b/builtins/src/main/java/org/jline/builtins/Nano.java
--- a/builtins/src/main/java/org/jline/builtins/Nano.java
+++ b/builtins/src/main/java/org/jline/builtins/Nano.java
@@
-import java.util.regex.Pattern;
+import com.google.re2j.Pattern;

If a dependency change is not acceptable, a fallback mitigation is to reject dangerous regex constructs or execute regex matching with a strict timeout, but that is weaker than replacing the backtracking engine.

Credits

This issue was identified by Michał Majchrowicz and Marcin Wyczechowski, members of the AFINE Team.

Severity

6.5 (Medium)


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

Show details on source website

JSON

To clipboard

{
  "affected": [
    {
      "package": {
        "ecosystem": "Maven",
        "name": "org.jline:jline-builtins"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "4.0.0"
            },
            {
              "fixed": "4.3.1"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "Maven",
        "name": "org.jline:jline-builtins"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "3.0.0"
            },
            {
              "fixed": "3.30.15"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-77421"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-1333"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-09-23T18:12:38Z",
    "nvd_published_at": null,
    "severity": "MODERATE"
  },
  "details": "### Summary\n\nWhen regex search mode is enabled in the JLine3 `nano` editor, the user-supplied\nsearch term is compiled directly as a Java regular expression with no timeout or\nbacktracking bound. A crafted pattern such as `(a+)+b` can hang the editor session\nthread at high CPU, causing a denial of service for that session.\n\n### Details\n\nIn `builtins/src/main/java/org/jline/builtins/Nano.java`, the search implementation\nuses `Pattern.LITERAL` only when regex mode is disabled. When regex mode is enabled,\nthe search term is compiled as a raw Java regex:\n\n```java\nPattern pat = Pattern.compile(\n        searchTerm,\n        (searchCaseSensitive ? 0 : Pattern.CASE_INSENSITIVE | Pattern.UNICODE_CASE)\n                | (searchRegexp ? 0 : Pattern.LITERAL));\n```\n\nThis regex is then applied to buffer content. Because Java\u0027s regex engine is\nbacktracking-based, nested-quantifier patterns can take exponential time on\nnon-matching input.\n\nAffected source location:\n- `builtins/src/main/java/org/jline/builtins/Nano.java`\n- `doSearch(String text)`\n\n### PoC\n\n1. Create a file containing a long run of `a` characters and open it in the JLine3\n   `nano` editor.\n2. Enable regex search mode with the editor\u0027s regex toggle.\n3. Start a search and enter the pattern `(a+)+b`.\n\nExpected result:\n- The editor stops responding.\n- The session thread consumes high CPU.\n\nReproduction environment:\n- JLine3 on x86_64 Linux\n- OpenJDK 25.0.2\n\n### Impact\n\nThis is a denial-of-service vulnerability caused by catastrophic regex backtracking.\nApplications embedding `org.jline:jline-builtins` and exposing the `nano` editor are\nimpacted. In local use, the user can hang their own session. In remote multi-user\ndeployments, an attacker can occupy a server worker thread indefinitely.\n\n### Suggested Fix\n\nThe preferred fix for the current git head is to use a linear-time regex engine for\nregex search mode while preserving literal matching behavior when regex mode is off.\n\nSuggested patch:\n\n```diff\ndiff --git a/builtins/pom.xml b/builtins/pom.xml\n--- a/builtins/pom.xml\n+++ b/builtins/pom.xml\n@@\n         \u003cdependency\u003e\n+            \u003cgroupId\u003ecom.google.re2j\u003c/groupId\u003e\n+            \u003cartifactId\u003ere2j\u003c/artifactId\u003e\n+            \u003cversion\u003e1.8\u003c/version\u003e\n+        \u003c/dependency\u003e\n+        \u003cdependency\u003e\n             \u003cgroupId\u003eorg.jline\u003c/groupId\u003e\n             \u003cartifactId\u003ejline-reader\u003c/artifactId\u003e\n         \u003c/dependency\u003e\n\ndiff --git a/builtins/src/main/java/org/jline/builtins/Nano.java b/builtins/src/main/java/org/jline/builtins/Nano.java\n--- a/builtins/src/main/java/org/jline/builtins/Nano.java\n+++ b/builtins/src/main/java/org/jline/builtins/Nano.java\n@@\n-import java.util.regex.Pattern;\n+import com.google.re2j.Pattern;\n```\n\nIf a dependency change is not acceptable, a fallback mitigation is to reject dangerous\nregex constructs or execute regex matching with a strict timeout, but that is weaker\nthan replacing the backtracking engine.\n\n### Credits\n\nThis issue was identified by Micha\u0142 Majchrowicz and Marcin Wyczechowski, members of the AFINE Team.",
  "id": "GHSA-ph9c-7hw9-vhhw",
  "modified": "2026-09-23T18:12:38Z",
  "published": "2026-09-23T18:12:38Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/jline/jline3/security/advisories/GHSA-ph9c-7hw9-vhhw"
    },
    {
      "type": "WEB",
      "url": "https://github.com/jline/jline3/pull/2012"
    },
    {
      "type": "WEB",
      "url": "https://github.com/jline/jline3/pull/2018"
    },
    {
      "type": "WEB",
      "url": "https://github.com/jline/jline3/commit/1d5fc3099e77938b971e197211cad2d4fbb17541"
    },
    {
      "type": "WEB",
      "url": "https://github.com/jline/jline3/commit/341ee69ccc57b7733c1b40d6993219b64b3206ae"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/jline/jline3"
    },
    {
      "type": "WEB",
      "url": "https://github.com/jline/jline3/releases/tag/4.3.1"
    },
    {
      "type": "WEB",
      "url": "https://github.com/jline/jline3/releases/tag/jline-3.30.15"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    }
  ],
  "summary": "JLine: ReDoS in Nano Editor Regex Search Mode"
}

Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.

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Action not permitted

CVE-2026-77421 (GCVE-0-2026-77421)

FKIE_CVE-2026-77421

GHSA-PH9C-7HW9-VHHW

Summary

Details

PoC

Impact

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Credits

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