Critical CVE-2026-111497 Out-of-Bounds Write Flaw in Google Brotli Decoder Impacts Broad Range of Environments

A severe vulnerability has been identified in the Google-developed Brotli decoder used for decompressing data in web communications and other applications. The flaw, tracked as CVE-2026-111497, allows out-of-bounds writes when processing specially crafted compressed data, potentially enabling arbitrary code execution, information disclosure, or denial of service. It carries a CVSS v4.0 base score of 9.2 and is rated Critical. Google has released patched versions 1.2.1, 1.1.1, and 1.0.10 of the library. Node.js incorporated the fix in its updates, while Microsoft issued an out-of-band patch for .NET on October 25, 2026, to address the issue. The vulnerability affects any environment relying on the Brotli C implementation for data decompression.

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A critical vulnerability has been discovered in the Google Brotli decoder, a widely used component for handling compressed data in web communications and numerous other environments. The issue, identified as CVE-2026-111497, resides in the C-language implementation of the decoder and can trigger an out-of-bounds write when processing maliciously crafted Brotli-compressed input.

Successful exploitation may result in arbitrary code execution, sensitive information leakage, or denial-of-service conditions. The vulnerability received a CVSS v4.0 base score of 9.2, placing it in the highest severity category of Critical.

Google has published corrected releases of the library: version 1.2.1, 1.1.1, and 1.0.10. Node.js developers referenced the CVE in their update notes, while Microsoft delivered an out-of-band security update on October 25, 2026, that resolves the flaw within the .NET framework.

Security researchers and coordination centers including JPCERT/CC and JVN have issued alerts highlighting the broad potential impact on any system that processes Brotli-encoded data.

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