Windows PHP Updated to Patch Critical Brotli Vulnerability CVE-2026-111497

The PHP development team has released updated Windows builds of PHP that bundle a patched version of the Brotli compression library. The update addresses CVE-2026-111497, a critical out-of-bounds write flaw in Google's Brotli decoder that can lead to remote code execution, information disclosure, or denial of service. The vulnerability carries a CVSS v4.0 base score of 9.2 and is rated Critical. It affects PHP environments where the cURL extension has automatic decompression of HTTP responses enabled, allowing Brotli decoding to occur. Although cURL automatic decompression is disabled by default, applications or HTTP client libraries may enable it. The fix updates the bundled Brotli component to version 1.2.1 in the releases PHP 8.5.12-1, 8.4.27-1, 8.3.36-1, and 8.2.35-1 published on October 26.

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The PHP development team has released updated Windows builds that address a serious vulnerability in the bundled Brotli compression library. The flaw, tracked as CVE-2026-111497, was discovered in the Brotli implementation provided by Google and allows an out-of-bounds memory write during decoding operations.

Successful exploitation can result in remote code execution, information leakage, or denial-of-service conditions. The vulnerability received a CVSS v4.0 base score of 9.2 and is classified as Critical.

The issue impacts Windows installations of PHP when the cURL extension is configured to automatically decompress HTTP responses. In such cases, the Brotli decoder processes untrusted data. Although automatic decompression is disabled in the default cURL settings, certain applications or HTTP client libraries may enable the feature, increasing exposure.

The corrected builds—PHP 8.5.12-1, 8.4.27-1, 8.3.36-1, and 8.2.35-1—replace the vulnerable Brotli component with version 1.2.1. Users are advised to apply the updates promptly.

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