Plain-English Summary
CVE-2026-111497 is a confirmed actively exploited vulnerability affecting Google Brotli. Tracked in the CISA Known Exploited Vulnerabilities (KEV) catalog as Google Brotli Unchecked Return Value Vulnerability, this flaw carries a CVSS base score of 8.8 (HIGH) and an EPSS exploitation probability of 82.64%. Because real-world threat actors are actively abusing this weakness in production environments, defenders and system administrators must treat patching or network-level isolation as an immediate priority rather than waiting for routine maintenance cycles.
According to defensive advisory data, Google Brotli contains an unchecked return value vulnerability that 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. Organizations running exposed or unpatched instances of Google Brotli face heightened operational risk, including unauthorized access, service disruption, or lateral movement depending on deployment architecture. Ransomware campaign association is currently recorded as 'Unknown'. If your environment exposes Brotli to untrusted networks, remote users, or partner integrations, prioritize verification of your current software build today.
Affected Products & Versions
| Vendor | Product | Weakness | Status |
|---|---|---|---|
| Brotli | CWE-252, CWE-787 | Affected (Verify Build) |
How to Fix & Patch
Workarounds & Temporary Mitigations
If an immediate maintenance window is unavailable for Google Brotli, reduce exposure by restricting administrative interfaces behind VPN or zero-trust access proxies, enforcing strict egress firewall rules, and enabling multi-factor authentication on all management endpoints. Review vendor release notes for temporary configuration flags or disabled-by-default mitigations.
Detection & Log Indicators
Defenders should audit perimeter firewall logs, authentication telemetry, and endpoint EDR alerts around Brotli processes. Look for unexpected child process execution, anomalous outbound connections, or sudden configuration changes. Search community Sigma detection repositories for CVE-2026-111497 or CWE-252, CWE-787 behavioral rules and correlate events against CISA's 2026-10-27 advisory timeline.
- Search SigmaHQ Rules for Google / Brotli detections.
- Review CISA KEV Catalog due date: 2026-11-10.
Frequently Asked Questions
Is CVE-2026-111497 actively exploited in the wild?
Yes. CISA added CVE-2026-111497 (Google Brotli) to the Known Exploited Vulnerabilities catalog on 2026-10-27, confirming active real-world exploitation.
How do I fix CVE-2026-111497 on Google Brotli?
Apply mitigations in accordance with vendor instructions, ensuring compliance with CISA’s BOD 26-04 Prioritizing Security Updates Based on Risk (see URL in Notes) guidance and CISA’s “Forensics Triage Requirements” (see URL in Notes). Follow applicable BOD 26-04 guidance for cloud services or discontinue use of the product if mitigations are unavailable. Stakeholders are responsible for evaluating each asset's internet exposure and ensuring adherence to BOD 26-04 patching guidelines. Check the official vendor advisory linked in the references section for exact version numbers.
What is the CVSS and EPSS score for CVE-2026-111497?
CVE-2026-111497 holds a HIGH rating (CVSS 8.8) and a FIRST EPSS exploitation probability of 82.64%.
What if I cannot patch Brotli immediately?
Isolate management interfaces from public internet access, enforce strict network segmentation, and monitor Brotli logs for anomalous activity until patched.
Official References
Last updated: 2026-11-13 · Defensive guidance only (no exploit code).