CVE-2026-111497
Google Brotli Unchecked Return Value Vulnerability
Google Brotli
A buffer overflow vulnerability in the Brotli decoder (c/dec/decode.c) in Google Brotli versions 1.0.3 through 1.2.0 on all platforms allows a remote unauthenticated attacker to corrupt adjacent decoder state memory, disclose sensitive memory contents, cause a denial of service, or potentially execute arbitrary code using a crafted Brotli-compressed stream. Users need to update any Brotli libraries or binaries between 1.0.3 through 1.2.0 to the latest available version: 1.0.10 or 1.1.1 or 1.2.1.
Exploitation status
CISA Known Exploited Vulnerabilities
Listed by CISA on 27 October 2026. US federal agencies were required to remediate it by 10 November 2026.
EPSS — exploitation probability
FIRST puts the probability of exploitation activity in the next 30 days at 82.6%, which is higher than 99.7% of all scored vulnerabilities. EPSS is a forecast of activity, not a measure of severity, and it is rescored daily.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Frequently asked questions
Is CVE-2026-111497 being exploited by ransomware groups?
No ransomware group in this database is currently recorded as exploiting CVE-2026-111497.
What does CVE-2026-111497 affect?
CVE-2026-111497 affects Google Brotli. A buffer overflow vulnerability in the Brotli decoder (c/dec/decode.c) in Google Brotli versions 1.0.3 through 1.2.0 on all platforms allows a remote unauthenticated attacker to corrupt adjacent decoder state memory, disclose sensitive memory contents, cause a denial of service, or potentially execute arbitrary code using a crafted Brotli-compressed stream. Users need to update any Brotli libraries or binaries between 1.0.3 through 1.2.0 to the latest available version: 1.0.10 or 1.1.1 or 1.2.1.
How severe is CVE-2026-111497?
CVE-2026-111497 is rated CRITICAL with a CVSS base score of 9.8. EPSS puts the probability of exploitation in the next 30 days at 82.6%, higher than 99.7% of all scored vulnerabilities. It is listed in the CISA Known Exploited Vulnerabilities catalog, with a federal remediation deadline of 10 November 2026.
How should organisations respond to CVE-2026-111497?
Apply the vendor patch for Google Brotli as the first priority, and treat any internet-facing instance as the most urgent. Because this vulnerability is associated with ransomware activity, also review whether the affected systems were reachable before patching, rather than assuming that patching alone closes the incident.