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Sandbox escape in Mozilla Networking component

IdentifiersCVE-2026-12297CWE-119

CVE-2026-12297 is a sandbox escape vulnerability in the Networking component of Mozilla products caused by incorrect boundary conditions. The issue affects Firefox, Firefox ESR, and Thunderbird builds prior to the fixed releases. While the available advisory text does not identify the exact vulnerable function or code path, it states that improper boundary handling in the Networking component can allow code or operations to cross intended sandbox isolation boundaries.

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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 can result in a sandbox escape, allowing an attacker to break out of the browser or mail client sandbox and perform actions outside the intended restricted execution environment. Advisory context for the affected Mozilla release trains indicates this may contribute to privilege escalation and, in broader exploit chains, facilitate arbitrary code execution or access beyond sandbox-imposed limits.

Mitigation

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

No vendor-provided workaround is specified in the available advisories. Until patching is complete, reduce exposure by enforcing least privilege, avoiding administrative user contexts, restricting access to untrusted websites and content, enabling exploit protection controls, and using host-based detection/prevention and application control where feasible.

Remediation

Patch, then assume compromise.

Upgrade affected Mozilla products to fixed versions: Firefox 152, Firefox ESR 140.12, Firefox ESR 115.37, Thunderbird 152, or Thunderbird 140.12, as applicable. Debian users should install the updated firefox-esr package version 140.12.0esr-1~deb13u1 or later where relevant.
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
MozillaFirefoxapplication
MozillaFirefox Esrapplication

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What this page doesn’t show

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Exposure mapping

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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

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Vendor-by-vendor mapping

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

Social activity

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