Microsoft and Palo Alto Networks have released fixes for CVE-2026-111497, an out-of-bounds write in the Google Brotli decoder, as the patch wave for the flaw spreads across runtimes, firewalls and Linux distributions. Neither company has found evidence of exploitation in the wild.
Node.js first disclosed the bug on October 21 as part of fixes for ten flaws. The developments since then are the vendor patches and new exposure figures.
Microsoft Ships Out-of-Band .NET Updates for Brotli CVE-2026-111497
On October 25, Microsoft published out-of-band updates for .NET 8, 9 and 10, .NET 11 RC3, Visual Studio and PowerShell. The flaw affects Brotli versions 1.0.3 through 1.2.0, and the fixed releases are 1.0.10, 1.1.1 and 1.2.1. Google rates the bug CVSS v4 9.2, while Microsoft’s advisory rates it CVSS 8.1 and describes exploitation as “more likely.”
A crafted Brotli stream can crash a process, leak memory and, in some cases, give an unauthenticated attacker code execution. The flaw has circulated under the nicknames Node2Shell, Broccoli2Shell and HTTP2Shell.
Which .NET Applications Are Actually Exposed to Brotli Decompression
Brotli decompression is not enabled by default in .NET. Applications are exposed only if they opt in through ASP.NET Core request decompression, HttpClient automatic decompression or the System.IO.Compression Brotli APIs. That opt-in requirement narrows the .NET exposure compared with products that always process Brotli input.
Palo Alto Networks Confirms PAN-OS 12.2, 12.1 and 11.2 Are Affected
On October 26, Palo Alto Networks confirmed that PAN-OS 12.2, 12.1 and 11.2, along with the Prisma Cloud Application Security Transporter Client, are affected, with a CVSS score of 9.2. PAN-OS 11.1 and 10.2 are not affected. The company listed hotfixes, and many of the builds match the hotfix builds it published for PHP2Shell, the PHP flaws patched earlier in the week.
Linux Distribution Patch Status Remains Uneven
Reporting indicates that Debian, Alpine and Amazon Linux have shipped fixes, while Ubuntu and SUSE had none and Red Hat had patched only partially. Red Hat says Firefox and Thunderbird may be affected. Updating the system Brotli library does not protect applications that bundle their own copy, so a patched distribution package does not settle the exposure for every installed program.
Wiz and Imperva Put Numbers and a Demonstration on the Risk
Wiz reported that 91% of cloud environments hold resources vulnerable to the flaw and that 82% have publicly exposed Node.js instances. Imperva demonstrated code execution on the official Node.js 24.22.0 Linux arm64 image, though not on every attempt. Public proof-of-concept code exists on GitHub.
Some experts have tempered alarm over the flaw, and the exposure for each product depends on whether it bundles Brotli and accepts compressed input from untrusted sources.
OpenAI Says the Root Bug Was Fixed in February Without a Release
OpenAI Codex Security found the issue during red-teaming. According to OpenAI, the underlying bug was corrected in the Brotli source code in February but was not recognized as a security flaw, and no new release followed. The fixed versions that vendors are now shipping therefore arrive months after the code change that addressed the defect.
For organizations that cannot patch immediately, the interim measure described in reporting is to block incoming Brotli-compressed requests at a proxy or firewall.
The Brotli library sits inside web servers, runtimes, firewalls and cloud services, which explains why one decoder bug has produced advisories from Microsoft, Palo Alto Networks, Node.js and Linux vendors within a week.
Other software named in reporting as affected includes Node.js, Python packages, Bun, Envoy and Istio. The Prisma Cloud Application Security Transporter Client appears on the same affected list as PAN-OS, and Palo Alto Networks lists hotfixes for each affected branch. Microsoft’s October 25 releases cover .NET, Visual Studio and PowerShell together, which gives administrators one set of updates for the Microsoft products involved.
