CVE-2026-77421

Status: Awaiting AnalysisMedium (6.5)—

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.

CVSS

Version: 3.1
Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Base score: 6.5

Exploitation probability (EPSS)

Probability of exploitation in the next 30 days: 0.43%
Percentile among all scored CVEs: 35
Score date: 10/5/2026

EPSS (Exploit Prediction Scoring System, FIRST) estimates how likely a vulnerability is to be exploited in the wild within 30 days. It complements CVSS (impact) and CISA KEV (confirmed exploitation).

🎯 ATT&CK techniques

How this vulnerability is exploited and what the attacker gains, in MITRE ATT&CK terms.

ExploitationT1210 Exploitation of Remote Serviceslateral movement72 %
Primary impactT1499.004 Application or System Exploitationimpact85 %

Servicio remoto (JLine en entornos multi-usuario) vulnerable a DoS por expresión regular maliciosa sin límite de backtracking; bloquea threads indefinidamente (CWE-1333).

Inferred by our analysis agent from the official description, CVSS vector and CWE, and checked by a supervisor. May contain errors.

🛡️ ATT&CK mitigations that cover these techniques

Vulnerability Scanning Threat Intelligence Program Privileged Account Management Network Segmentation Filter Network Traffic Disable or Remove Feature or Program

Affected technologies (1)

⚠ AI-inferred from the description — NVD hasn't analyzed this CVE yet, these aren't verified CPEs.

Jline — Jline^AI

CWEs

CWE-1333

References

Raw JSON (NVD)

Show

{
  "id": "CVE-2026-77421",
  "cveTags": [],
  "metrics": {
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "id": "CVE-2026-77421",
          "role": "CISA Coordinator",
          "options": [
            {
              "exploitation": "none"
            },
            {
              "automatable": "no"
            },
            {
              "technicalImpact": "partial"
            }
          ],
          "version": "2.0.3",
          "timestamp": "2026-09-23T19:05:07.485942Z"
        }
      }
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    "cvssMetricV31": [
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        "type": "Secondary",
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        "cvssData": {
          "scope": "UNCHANGED",
          "version": "3.1",
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          "attackVector": "NETWORK",
          "baseSeverity": "MEDIUM",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H",
          "integrityImpact": "NONE",
          "userInteraction": "NONE",
          "attackComplexity": "LOW",
          "availabilityImpact": "HIGH",
          "privilegesRequired": "LOW",
          "confidentialityImpact": "NONE"
        },
        "impactScore": 3.6,
        "exploitabilityScore": 2.8
      }
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  "affected": [
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      "source": "security-advisories@github.com",
      "affectedData": [
        {
          "vendor": "jline",
          "product": "jline3",
          "versions": [
            {
              "status": "affected",
              "version": ">= 3.0.0, < 3.30.15"
            },
            {
              "status": "affected",
              "version": ">= 4.0.0, < 4.3.1"
            }
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  "published": "2026-09-23T19:19:15.700",
  "references": [
    {
      "url": "https://github.com/jline/jline3/commit/1d5fc3099e77938b971e197211cad2d4fbb17541",
      "source": "security-advisories@github.com"
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      "source": "security-advisories@github.com"
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    {
      "url": "https://github.com/jline/jline3/pull/2012",
      "source": "security-advisories@github.com"
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      "url": "https://github.com/jline/jline3/pull/2018",
      "source": "security-advisories@github.com"
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      "url": "https://github.com/jline/jline3/releases/tag/4.3.1",
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      "url": "https://github.com/jline/jline3/releases/tag/jline-3.30.15",
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      "url": "https://github.com/jline/jline3/security/advisories/GHSA-ph9c-7hw9-vhhw",
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  "vulnStatus": "Awaiting Analysis",
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      "description": [
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  "descriptions": [
    {
      "lang": "en",
      "value": "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."
    }
  ],
  "lastModified": "2026-09-30T16:44:39.840",
  "sourceIdentifier": "security-advisories@github.com"
}