A vulnerability in Google’s Brotli data-compression library could let hackers take control of vulnerable systems, crash applications or potentially access sensitive information. Because Brotli is built into widely used software and cloud services, the flaw could affect websites and apps people use every day, potentially disrupting services or putting data at risk.
The vulnerability, tracked as CVE-2026-111497, affects software that uses Brotli to decompress data. Google committed a fix to its source repository in February 2026 but did not issue a formal release containing the correction until 21 October.
Security firm Wiz reported that 91 per cent of cloud environments contain resources affected by the flaw, while 82 per cent have Node.js systems directly exposed to the public internet. Khai Tran and Sylvie Mayer of OpenAI’s Codex Security team discovered and reported the vulnerability while testing the company’s internal systems.
Faulty Error Handling Causes Memory Corruption
The flaw sits in Brotli’s data-decompression process. When the software encounters malformed input, it incorrectly treats the problem as a request for more data rather than a fatal error.
It continues adding incoming bytes to a small internal storage area designed to hold just eight bytes. This can overwrite memory beyond the allocated space, potentially creating an opening for attackers.
OpenAI said an unpatched server processing malformed input could be taken over. An unpatched program, including the command-line tool curl, could also be compromised when receiving a response from a malicious server. The memory corruption could additionally expose sensitive information without requiring a password or other credentials.
Imperva’s Red Team demonstrated code execution on an unpatched Node.js build running on Linux ARM64. Researchers at JFrog also demonstrated crashes in the ClickHouse database and a processing loop that exhausted the processor in the Python package pyarrow.
Security Fix Went Unreleased for Eight Months
The correction was committed on 27 February 2026, but no new library version containing it was released at the time. OpenAI said the delay occurred because maintainers did not initially recognise that the code change addressed a security vulnerability. Its security tools identified the significance of the fix.
The vulnerability can affect applications that bundle their own copies of Brotli. These applications may require separate updates or rebuilds, even if developers do not use the library directly.
Software identified as affected includes Node.js, Bun, Microsoft .NET, Envoy, Istio, ClickHouse, FFmpeg and Apache Arrow, alongside Go and Python packages. Go versions have built-in safety checks that prevent the memory overwrite. However, they can still crash, potentially interrupting web requests without allowing an attacker to take control.
Organisations Urged To Update Affected Systems
Google assigned the vulnerability a score of 9.2 out of 10, classifying it as critical. Node.js rated it high, while Red Hat and Microsoft each gave it a score of 8.1. Red Hat noted that no reliable public exploit enabling remote code execution had been found. Microsoft said ASP.NET Core and HttpClient do not enable Brotli decompression by default.
Organisations are advised to update affected software, including Node.js versions 22.23.4, 24.22.1 and 26.12.1, as well as Go Brotli v1.2.7. They should also rebuild container images and self-contained programs that embed vulnerable code.
Where patching is not immediately possible, organisations may reduce exposure by disabling vulnerable Brotli decompression paths or rejecting Brotli-encoded requests at an appropriate proxy. These measures are temporary mitigations.