On October 21, 2026, the Node.js Project published a security advisory for CVE-2026-111497, an out-of-bounds write in the Brotli decoder bundled with Node.js. The vulnerability affects the Node.js 26.x, 24.x, and 22.x release lines. Node.js rates the issue High, while Google, the CVE Numbering Authority (CNA), gives it a critical CVSSv4 score of 9.2.
An attacker who can supply Brotli data that an application decompresses with node:zlib can corrupt process memory. According to Node.js, this corruption can lead to a process crash, disclosure of sensitive process memory, or remote code execution. Exposure therefore depends on whether an application passes attacker-controlled compressed data to the affected decoder.
On October 27, 2026, CVE-2026-111497 was added to the U.S. Cybersecurity and Infrastructure Security Agency's (CISA) list of known exploited vulnerabilities (KEV), based on evidence of active exploitation. Given the vulnerability's potential to disclose memory or enable remote code execution (RCE), Rapid7 recommends that organizations prioritize remediation.
Technical overview
CVE-2026-111497 is classified as an out-of-bounds write (CWE-787) and an unchecked return value (CWE-252). Per the vendor advisory, the decoder handled an invalid Brotli block switch as a temporary need for more input instead of a permanent format error. The streaming decoder then continued appending input bytes to an eight-byte internal buffer, allowing malformed input to write beyond the buffer and corrupt process memory.
The vulnerability originates in Google Brotli, which the affected Node.js release lines bundle as a dependency. The CVE record identifies affected upstream Brotli ranges on all platforms as versions 1.0.3 before 1.0.10, 1.1.0 before 1.1.1, and 1.2.0 before 1.2.1. The Node.js Project remediated its bundled decoder in the fixed Node.js releases listed below.
Because CVE-2026-111497 affects the upstream Google Brotli decoder, its reach is not limited to Node.js. Vendor and project advisories have also identified affected implementations in Bun, Python's Brotli and brotlicffi packages, .NET, Envoy and Istio, brotli4j, and operating-system packages. Affected versions, default exposure, and remediation vary by product; the presence of an affected decoder does not by itself establish exposure unless an application processes attacker-controlled Brotli data. Organizations should consult the relevant downstream vendor or distribution advisories to identify affected versions, assess exposure, and determine appropriate remediation.
Mitigation guidance
Vendor-supplied security updates are available to remediate CVE-2026-111497. Organizations running an affected Node.js release should upgrade on an urgent basis, outside of normal patch cycles:
Node.js 22.x releases before 22.23.4 are affected; upgrade to 22.23.4 or later.
Node.js 24.x releases before 24.22.1 are affected; upgrade to 24.22.1 or later.
Node.js 26.x releases before 26.12.1 are affected; upgrade to 26.12.1 or later.
The vendor states that end-of-life Node.js release lines should also be treated as affected when a security release occurs. Organizations using an end-of-life release should migrate to a supported, fixed release line. Node.js has not published a vendor-supported workaround; if an immediate upgrade is not possible, Rapid7 recommends restricting or disabling application paths that decompress untrusted Brotli data as a temporary exposure-reduction measure.
For the latest mitigation guidance, please refer to the Node.js security advisory.
Rapid7 customersExposure Command, Vulnerability Management, and Nexpose
Exposure Command, Vulnerability Management, and Nexpose customers can assess exposure to CVE-2026-111497 with an authenticated vulnerability check for Linux, macOS, and Windows, available in the October 26 content release.
Updates
October 26, 2026: Initial publication.
- October 26, 2026: Updated the Exposure Command, Vulnerability Management, and Nexpose section to reflect coverage availability.
- October 27, 2026: Updated Overview to add a reference to CVE-2026-111497 being added to the CISA KEV list.
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CVE-2026-111497: Critical out-of-bounds write in the Node.js Brotli decoder