CVE-2026-111497 Google · Brotli

Node.js / Google Brotli - Decoder Out-of-Bounds Write

Vulnerability at a glance

Severity, exploitation likelihood & attack requirements

CVSS v4.0 severity
9.2Critical
EPSS · exploitation likelihood
Not available No score available
EPSS trend
UnavailableNo comparable history
Known exploitation
Not in KEV CISA KEV catalog Absence does not establish safety
Attack vector
NetworkRemotely reachable
Attack complexity
LowFewer obstacles to exploitation
Privileges required
NoneNo authentication required
User interaction
NoneNo user action needed
Exploit availability & maturity
Not scored Availability not established No explicit exploit maturity assessment View exploit evidence
How to read the colors & trend
Higher exposureElevatedModerateLower exposureUnknown / unassessed

CVSS colors follow its reported severity. Attack-factor colors describe each requirement, not an overall risk rating. Gray also covers absence from KEV; absence does not establish safety.

EPSS display bands: below 1% blue, 1–10% amber, 10–50% orange, 50% and above red. These are presentation bands, not FIRST severity categories. The trend compares daily EPSS probabilities, not percentile ranks; “pp” means percentage points. The sparkline shows relative movement, with its vertical scale fitted to the observed scores.

Already protected by existing Atomicorp rules No new CVE-specific rule required.

Atomicorp ModSecurity protection

Protected by Atomicorp rules

Atomicorp ModSecurity rules block attacks exploiting this vulnerability. Keep your rules current.

By targeting underlying attack techniques and CWE weakness classes, existing rules can protect against newly disclosed vulnerabilities. Rule changes are regression-tested against attack and false-positive corpora.

1 rule identified View rules & research details →

WAF protection does not change the CVSS or EPSS score. Keep your software patched and your Atomicorp rules current.

CISA SSVC assessment

CISA ADP · Assessed 2026-10-23 · SSVC 2.0.3

Exploitation
None reported
Automatable
No
Technical Impact
Total

Stakeholder-Specific Vulnerability Categorization records CISA’s assessment of exploitation, automation, and technical impact. “None reported” reflects the assessment date; it does not establish that no exploit exists. View SSVC source details.

On this page

Why existing Atomicorp rules protect this CVE

Existing rule 340362 provides protection against CVE-2026-111497 by refusing compressed request bodies. No new CVE-specific rule is required. This existing control interrupts delivery of a crafted Brotli stream to a server application.

The protection finding is based on manual engineering review of the published vulnerability and the current rule. Atomicorp has not performed a CVE-2026-111497 PoC or exploit replay for this finding. Rule 340362 is recorded as a reviewed blocking rule; this article does not claim an observed exploit interception.

What the vendors disclosed

CVE-2026-111497 is an out-of-bounds write in Google’s Brotli decoder. Malformed compressed data can corrupt memory, potentially causing a crash, information disclosure or remote code execution. Node.js includes the decoder and addressed the issue in its October 2026 security releases for the 22.x, 24.x and 26.x lines.

Google’s CNA assessment assigns CVSS v4.0 9.2 (Critical). The Node.js release post labels the issue High. These are separately attributed vendor assessments; the protection finding does not lower the vulnerability’s score.

The Node.js release post , GitHub advisory and CVE record provide the upstream vulnerability and update information.

CVE Details

  • Protection status: Protected by Atomicorp rules · About protection statuses
  • CVE: CVE-2026-111497
  • Name: Node.js / Google Brotli - Decoder Out-of-Bounds Write
  • Severity: Critical
  • CVSS: 9.2 (v4.0) (Critical)
  • CVSS version: 4.0
  • CVSS source: Google CNA
  • CVSS vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
    • Attack vector: Network
    • Attack complexity: Low
    • Attack requirements: Present
    • Privileges required: None
    • User interaction: None
    • Vulnerable-system confidentiality: High
    • Vulnerable-system integrity: High
    • Vulnerable-system availability: High
    • Subsequent-system confidentiality: Negligible
    • Subsequent-system integrity: None
    • Subsequent-system availability: None
    • Safety: Not defined
  • CWE: CWE-252 , CWE-787
  • Vendor: Google
  • Vulnerable product: Brotli
  • CVE published: 2026-10-22
  • CVE last modified: 2026-10-24
  • Latest Update: 2026-10-24
  • Reviewed Rule IDs: 340362
  • Reviewed rules with current blocking actions: 340362
  • Request surfaces inspected: Request headers
Technical vulnerability details · CVSS assessments, exploit evidence & CPE data

CVSS assessments

CVSS v4.0 · cve-coordination@google.com

  • Base score: 9.2
  • Base severity: CRITICAL
  • Assessment type: Secondary
  • Source identifier: cve-coordination@google.com
  • Full vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
    • Attack vector: Network
    • Attack complexity: Low
    • Attack requirements: Present
    • Privileges required: None
    • User interaction: None
    • Vulnerable-system confidentiality: High
    • Vulnerable-system integrity: High
    • Vulnerable-system availability: High
    • Subsequent-system confidentiality: Negligible
    • Subsequent-system integrity: None
    • Subsequent-system availability: None
    • Safety: Not defined
  • Exploit maturity: Not scored

Exploitability and impact subscores describe the vulnerability’s technical characteristics. Exploit maturity describes the reported state of exploitation; these are separate measures.

Assessment source: NVD record · CVE record

CISA SSVC assessments

These are CISA’s published decision points at the assessment time. They are not a complete organization-specific prioritization decision.

  • Provider: CISA ADP
  • Provider identifier: 134c704f-9b21-4f2e-91b3-4a467353bcc0
  • SSVC version: 2.0.3
  • Role: CISA Coordinator
  • Assessment timestamp: 2026-10-23T00:00:00+00:00
  • Exploitation: none
  • Automatable: no
  • Technical Impact: total
  • Source: CISA ADP in the CVE record

Vulnerable CPE configurations

No vulnerable CPE configurations are supplied in the current NVD record. See the affected-product information and vendor guidance on this page.

Vulnerability Description

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.

  1. Maintain the reviewed Atomicorp rules. Keep your Atomicorp commercial rules current and confirm that the reviewed rules (340362 ) have not been locally disabled. Atomicorp commercial rules are enabled by default. If you use Atomic WAF, review the applicable policy and rule settings.

  2. Apply the vendor’s remediation. WAF protection is defense in depth and does not replace upgrading or following the affected vendor’s guidance.

    • Affected versions: Google Brotli versions earlier than 1.0.10.
    • Affected versions: Google Brotli versions earlier than 1.1.1.
    • Affected versions: Google Brotli versions earlier than 1.2.1.
    • Recommended upgrade: Upgrade Google Brotli to 1.0.10 or later.
    • Recommended upgrade: Upgrade Google Brotli to 1.1.1 or later.
    • Recommended upgrade: Upgrade Google Brotli to 1.2.1 or later. Upgrade Node.js to 22.23.4, 24.22.1 or 26.12.1, as appropriate for the supported release line, or a later release containing the fix. See the Node.js security release post .

    Update Google Brotli libraries to the fixed version for the maintained branch: 1.0.10, 1.1.1 or 1.2.1, or a later fixed release. Follow the applicable package vendor’s security guidance, rebuild or redeploy applications that bundle the library, and restart updated services.

    Keep Atomicorp rules current and complete the vendor upgrades. Confirm the deployed runtime and dependency versions, then verify normal application operation.

  3. Validate after changes. Confirm rule updates are current, review WAF events for the affected application, and test application behavior after vendor upgrades, mitigations, or local policy changes.

Research Notes

Atomicorp WAF protections are designed around attack techniques and exploit behaviors, allowing existing protections to apply across multiple vulnerabilities without requiring a unique rule for every CVE.

Public Vulnerability References

Test or Research Source

Research Note Context

This research note documents exploit-technique analysis associated with this vulnerability and references Atomicorp WAF protections observed during engineering review, testing, or validation activities.

Atomicorp security controls are generally designed to identify and mitigate attack techniques and exploit behaviors rather than individual CVE identifiers. As a result, protections developed for one vulnerability may also apply to related attack variants and future vulnerabilities using similar techniques.

Learn More

Atomicorp develops commercially supported security technologies for web applications, servers, endpoints, workloads, and legacy enterprise platforms.

Organizations interested in protecting systems against exploit techniques associated with vulnerabilities such as this one can learn more about:

  • Atomic ModSecurity Rules: commercially maintained WAF rules for ModSecurity deployments, including protections for web attacks, bots, scanners, malware, exploitation attempts, and emerging vulnerability classes.
  • Atomic WAF: an enterprise web application firewall with Atomicorp rules, centralized management, reporting, authentication controls, and operational tooling.
  • Atomic ModSecurity Integrator: a special licensing option for MSPs, MSSPs, OEMs, VARs, reverse proxy providers, and other integrators who want to incorporate Atomicorp ModSecurity rule technology into their own products or services.
  • Atomic OSSEC: an enterprise OSSEC-based intrusion detection, compliance, and security monitoring platform.
  • Atomic Protector: workload protection for Linux, web, cloud, data center, and hybrid environments.

For additional information, product evaluations, or technical discussions, visit https://www.atomicorp.com/ or https://modsecurity.io/ .