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Same Origin Policy Bypass in Google Chrome Extensions

IdentifiersCVE-2026-12456CWE-20

CVE-2026-12456 is a high-severity vulnerability in the Extensions component of Google Chrome prior to 149.0.7827.155. The issue is described as an inappropriate implementation / insufficient validation of untrusted input in Chrome Extensions. According to the provided advisory context, an attacker who convinces a user to install a crafted malicious Chrome extension can exploit the flaw to bypass the browser's same origin policy. The vulnerability therefore resides in extension handling or enforcement logic that fails to properly validate untrusted extension-controlled input or behavior, allowing extension-originated actions to circumvent intended origin isolation restrictions.

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ANALYST BRIEF

Impact, mitigation & remediation

What it means. What to do now. Patch path, mitigations, and the assume-compromise checklist.

Impact

What an attacker gets, and what they’ve been doing with it.

Successful exploitation allows a malicious extension to bypass Chrome's same origin policy. This can undermine browser security boundaries intended to isolate content from different origins, potentially enabling unauthorized cross-origin access to sensitive data or privileged interactions that should normally be blocked. Depending on the permissions granted to the extension and the victim's browsing context, this could facilitate sensitive information disclosure and broader security restriction bypass within the browser.

Mitigation

If you can’t patch tonight, do this now.

Until patched versions are fully deployed, reduce exposure by preventing installation of untrusted or unnecessary browser extensions, enforcing enterprise extension allowlists, restricting extension installation to trusted sources, and monitoring managed environments for unauthorized extension deployment. The provided advisories do not describe a product-level workaround other than updating.

Remediation

Patch, then assume compromise.

Update Google Chrome to version 149.0.7827.155 or later. For Microsoft Edge (Chromium-based), update to version 149.0.4022.80 or later. For Debian Chromium, upgrade to the fixed package versions identified in the advisory, including 149.0.7827.155-1~deb13u1 for Debian stable (trixie) and 149.0.7827.155-1~deb12u1 for Debian oldstable (bookworm).
PUBLIC EXPLOITS

Exploits

No public exploits tracked yet. Mallory keeps watching.

VALID 0 / 0 TOTALView more in app

No public exploit code observed for this vulnerability.

EXPOSURE SURFACE

Affected products & vendors

Products and vendors Mallory has correlated with this vulnerability. Open in Mallory to drill down to specific CPE configurations and version ranges.

VendorProductType
GoogleChromeapplication
Microsoft CorporationEdgeapplication

Vendor-confirmed product mapping. Mallory continuously reconciles this list against your asset inventory.

ACTIVITY FEED

Recent activity

6 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.

6 SOURCESView more in app
What this page doesn’t show

The version that knows your environment.

This page is what’s public. Mallory adds the parts that aren’t: which of your assets are affected, which adversaries are exploiting it right now, which detections to deploy, and what to do tonight.
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Exposure mapping

Query your assets running an affected version, and investigate the blast radius.

Threat actor evidence

Every observed campaign linking this CVE to a named adversary.

Associated malware

Malware families riding this exploit, with evidence and IOCs.

Detection signatures

YARA, Sigma, Snort, and vendor rules, auto-deployed to your SIEM.

Vendor-by-vendor mapping

Cross-references every affected SKU, including bundled OEM variants.

Social activity1

Community discussion across Reddit, Mastodon, and other social sources.

EXTERNAL REFERENCES
MITRE CVE
cve.org · CVE-2026-12456
NVD
nvd.nist.gov/vuln/detail/CVE-2026-12456
MITRE CWE · CWE-20
cwe.mitre.org