Vulnerability report

Exploitation attempts observed Confirmed confidence In CISA KEV

CVE-2026-111497

Out-of-Bounds Write in Google Brotli Decoder

Google / Brotli · affected before 1.0.10

Watch CVE-2026-111497 Browse KEV feed
Severity
CVSS 9.2 · Critical
Confidence
Confirmed
Exploit status
Observed in sensors
EPSS
55.5%
First observed
27 Oct 2026
Last observed
27 Oct 2026

Decision summary

What security teams need to know first

Direct answers before the deeper technical record.

What it is

CVE-2026-111497 is an unauthenticated Out-of-Bounds Write in Google Brotli Decoder. 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...

Have exploitation attempts been observed?

Yes. Previdian sensors have observed 1 exploitation attempt, 1 unique attacker IP, and 1 country targeting CVE-2026-111497. First observed Oct 27, 2026. Listed in CISA KEV. Also reported by third-party sources. Confidence is confirmed.

Who is affected?

Google / Brotli affected before 1.0.10.

What should we do?

Patch immediately, validate internet-facing exposure, and monitor for matching requests.

Overview

Out-of-Bounds Write in Google Brotli Decoder

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.

Google Affected
Brotli github.com/google/brotli
Before 1.0.10 Before 1.1.1 Before 1.2.1
View vendor advisory (opens in new tab)
Published
22 Oct 2026
Attempts Observed Since
27 Oct 2026
Attack vector
Remote
Complexity
Low
Privileges
None
User interaction
None

Tags

cisa

CVE References

  • CVE Record CVE.org · CVE Record https://www.cve.org/CVERecord?id=CVE-2026-111497
  • Patch — nodejs.org nodejs.org · Patch https://nodejs.org/en/blog/vulnerability/october-2026-security-releas...
  • GitHub — andybalholm/brotli github.com · Third-Party Advisory https://github.com/andybalholm/brotli/releases/tag/v1.2.7

Exploitation evidence

Evidence of exploitation attempts

Third-party attestation and first-party sensor observation are shown separately so teams can judge the evidence chain.

Exploitation attempts observed in the wild

Previdian sensor

Recorded 27 Oct 2026

Previdian sensors observed exploitation attempts targeting this vulnerability before a third-party report.

Exploitation attempts observed

Previdian sensor

First observed 27 Oct 2026

Previdian sensors observed exploitation attempts targeting this vulnerability.

Proof of concept available

GitHub

Recorded 22 Oct 2026

Public scanner or PoC coverage increases practical exploitability.

Known exploited vulnerability sources

Per-source evidence links for KEV attestations are available through the Previdian Pro API.

Learn about Pro API access
Source Added
CISA First 2026-10-27 20:01 UTC
Previdian Sensors 2026-10-27 20:05 UTC
Tenable Blog 2026-10-27 20:20 UTC
The Hacker News 2026-10-28 06:33 UTC

Operational indicators for this CVE are listed under Detection.

Sensor telemetry

Previdian Sensor Observations

Previdian sensor observations are exploitation attempts targeting this vulnerability. They do not show that the target was vulnerable or that the attempt succeeded. The cards and chart show volume, unique attackers, and daily activity.

1

Attempts observed

1

Unique attacker IPs

1

Attacker countries

US

1

Sensors observed

CVE-2026-111497 exploitation attempts over the last 7 days

Daily events observed by Previdian sensors

Updated 28 Oct 2026

0
0
0
0
0
1
0
22 Oct 23 Oct 24 Oct 25 Oct 26 Oct 27 Oct 28 Oct

First observed 27 Oct 2026 · Last observed 27 Oct 2026

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Detection

Operational artifacts and observed signals

Make the evidence actionable in scanner, SOC, and edge-control workflows.

Observed signals

Request targets
User-Agents
Callback hosts
1
1
0

Request targets and User-Agents available in Pro. Callback host details available in Enterprise.

Scanner coverage

No scanner integrations recorded yet.

Virtual patch status

No Previdian virtual patch is currently available. Future rules ship for ModSecurity, Cloudflare, and AWS WAF.

Learn about virtual patches →

Attacker IP Indicators

Attacker IP indicators observed · available in Pro and Enterprise.

Sensor-derived attacker IP indicators are available to Pro and Enterprise accounts under Detection and through the Pro API.

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Risk and context

Severity, weaknesses, and research context

CVSS v4.0

9.2 Critical

Potential damage if exploited. Separate from whether attackers are using it.

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

EPSS

55.5%

Estimated chance of exploitation in the next 30 days. Previdian's warning comes from evidence, not this score.

Weaknesses

Unchecked Return Value CWE-252 Out-of-bounds Write CWE-787

Recent mention · The Hacker News

Adobe Commerce PolyShell Attacks Breach Hundreds of Stores as Brotli Exploit Traffic Emerges

Ravie LakshmananOct 28, 2026Vulnerability / Web Security The U.S. Cybersecurity and Infrastructure Security Agency (CISA) on Tuesday added two vulnerabilities impacting Adobe Commerce and Magento, and Google's Brotli decoder library to its Known Exploited Vulnerabilities...

Read full advisory

All Mentions

Recent mention · The Hacker News

Adobe Commerce PolyShell Attacks Breach Hundreds of Stores as Brotli Exploit Traffic Emerges

The Hacker News · 28 Oct 2026

Ravie LakshmananOct 28, 2026Vulnerability / Web Security The U.S. Cybersecurity and Infrastructure Security Agency (CISA) on Tuesday added two vulnerabilities impacting Adobe Commerce and Magento, and Google's Brotli decoder library to its Known Exploited Vulnerabilities (KEV) catalog, citing evidence of active exploitation. The vulnerabilities are listed below - CVE-2026-111497 (CVSS score: 9.2) - An unchecked return value vulnerability in Google Brotli that could allow a remote unauthenticated attacker to corrupt adjacent decoder state memory, disclose sensitive memory contents, cause a...

Recent mention · Cisco Security Advisory

Vulnerabilities in node.js Affecting Cisco Products: October 2026

Cisco Security Advisory · 27 Oct 2026

On October 21, 2026, Node.js announced the availability of fixes for multiple vulnerabilities across the following supported release lines: 22.x, 24.x, and 26.x.  These vulnerabilities impact critical operations such as the Brotli decoder, DNS resolution, and TLS certificate validation. The vulnerabilities pose risks for remote code execution and traffic interception. For more information, see Node.js Security Release.  The following vulnerabilities have a Security Impact Rating (SIR) of High and are addressed in this advisory: CVE-2026-111497 - Brotli decoder out-of-bounds write;...

Recent mention · FortiGuard Center - Outbreak Alerts

Node2Shell Remote Code Execution

FortiGuard Center - Outbreak Alerts · 27 Oct 2026

CVE-2026-111497 is an out-of-bounds write vulnerability in Google's Brotli decoder, a component used to decompress data encoded with the Brotli compression algorithm. Brotli is widely used in web communications and is incorporated into software libraries, runtimes, and HTTP clients, including Node.js.

Recent mention · Tenable Blog

Brotli2Shell: Frequently asked questions for Google Brotli decoder vulnerability (CVE-2026-111497)

Tenable Blog · 27 Oct 2026

Researchers have demonstrated remote code execution through CVE-2026-111497, an out-of-bounds write in Google's Brotli decoder library, and public proofs-of-concept (PoCs) are available. Software that uses the decoder includes Node.js, .NET, Bun, Envoy Proxy, Istio, Python HTTP clients and PHP for Windows.Key TakeawaysCVE-2026-111497, known as Brotli2Shell and by several other names, is an out-of-bounds write in Google's Brotli decoder library that Google, the CVE Numbering Authority (CNA), scored 9.2 under CVSSv4.0.Any application that decompresses attacker-controlled data with a...

Recent mention · F5 Security Advisories

K000163902: Google Brotli Decoder vulnerability CVE-2026-111497

F5 Security Advisories · 27 Oct 2026

Security Advisory 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. (CVE-2026-111497) This CVE was previously included in K000163874:...

Recent mention · The Hacker News

CISA Confirms Active Exploitation of Two PHP2Shell Flaws Enabling Remote Code Execution

The Hacker News · 27 Oct 2026

Ravie LakshmananOct 27, 2026Vulnerability / Web Security The U.S. Cybersecurity and Infrastructure Security Agency (CISA) on Monday confirmed active exploitation of the recently patched PHP2Shell flaws by adding them to its Known Exploited Vulnerabilities (KEV) catalog. The PHP vulnerabilities, both rated 9.2 on the CVSS scoring system, facilitate unauthenticated remote code execution on affected deployments - CVE-2026-109618 - An out-of-memory corruption vulnerability that allows for unauthenticated remote code execution. CVE-2026-109619 - A stale internal request-state vulnerability...

Recent mention · Palo Alto Networks Security Advisories

CVE-2026-111497 Portfolio Status: Impact of Brotli Vulnerability (CVE-2026-111497) on Palo Alto Networks Products (Severity: CRITICAL)

Palo Alto Networks Security Advisories · 26 Oct 2026

Recent mention · TheRegister

Microsoft releases emergency .NET security fixes for Google Brotli bug

TheRegister · 26 Oct 2026

Redmond joins growing list of software maintainers scrambling to patch compression flaw

Recent mention · The Hacker News

PHP Issues Second Windows Security Update in Five Days to Fix Brotli Code Execution Flaw

The Hacker News · 26 Oct 2026

PHP has rebuilt its official Windows packages for PHP 8.2 through 8.5 to fix CVE-2026-111497, a flaw in the Brotli compression library that the packages include. The flaw can let an attacker corrupt memory and potentially run code. PHP says the flaw can be reached through the cURL extension when the extension decompresses HTTP responses automatically. cURL leaves that off by default, but

Recent mention · Rapid7

CVE-2026-111497: Critical out-of-bounds write in the Node.js Brotli decoder

Rapid7 · 26 Oct 2026

OverviewOn 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...

Potential Proof of Concepts

These PoCs are unverified and could contain malware. Use at your own risk.

Hika-sec/http2shell-CVE-2026-111497

github · Created 2026-10-25 18:05:02 UTC · 3 stars · AI assessment 82%

PoC for CVE-2026-111497, a buffer overflow in Google Brotli 1.0.3–1.2.0 that may cause memory corruption, data disclosure, DoS, or RCE when processing crafted compressed data.

Arkango/CVE-2026-111497

github · Created 2026-10-23 14:34:49 UTC · 0 stars · AI assessment 82%

CVE-2026-111497 (Node2Shell) — Node.js Brotli decoder OOB heap write. Independent research: exploit code, Docker labs, Express RCE gap analysis.

TheFool-TAROT/CVE-2026-111497-brotli-pwn

github · Created 2026-10-22 16:30:53 UTC · 0 stars · AI assessment 84%

CVE-2026-111497: Node.js Brotli decoder OOB write — analysis, PoC, Docker lab

dimasma0305/CVE-2026-111497-POC

github · Created 2026-10-22 04:08:28 UTC · 1 stars · AI assessment 86%

Reproducible local Brotli decoder proof for CVE-2026-111497 with a self-checking tuned RCE harness

CVE Record exploit — imperva.com

cve · Created Unknown

Timeline

From disclosure to observed exploitation attempts

  1. 06:33 UTC

    KEV confirmed by The Hacker News

    Exploitation attempts reported by an external source

  2. 20:20 UTC

    KEV confirmed by Tenable Blog

    Exploitation attempts reported by an external source

  3. 20:01 UTC

    Added to CISA KEV

    Listed in the CISA Known Exploited Vulnerabilities catalog

  4. 20:01 UTC

    Indicator of compromise added

    Indicators of compromise recorded

  5. 20:01 UTC

    Observed by Previdian sensors

    Previdian sensors observed exploitation attempts targeting this vulnerability.

  6. 14:20 UTC

    Added to the Previdian watchlist

    Pro and Enterprise Watch users had 5 days of early warning before CISA KEV. Also 5 days before Previdian confirmed it as a KEV.

  7. 13:35 UTC

    CVE published

    Vulnerability disclosed publicly

  8. 04:08 UTC

    Public PoC available

    Public proof-of-concept code published

  9. 09:58 UTC

    CVE ID reserved

    Identifier reserved by the CNA

Pro API

Automate this intelligence

Confidence, exploit status, sensor telemetry, PoCs, scanner integrations, mentions, and tags are available programmatically for VM, SOC, and CTI workflows.

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  • Evidence confidence and provenance
  • First-party sensor telemetry
  • PoC and scanner references
  • Affected versions and enrichment
  • Automation-ready JSON delivery

GET /api/v2/pro/kevs/CVE-2026-111497

Sample API response 
{
  "cve_id": "CVE-2026-111497",
  "confidence": "Confirmed",
  "cvss_score": 9.2,
  "cvss_estimated": false,
  "epss_score": 0.55483,
  "exploit_status": {
    "exploited_in_the_wild": true,
    "active_exploitation_observed": true
  },
  "sensor_telemetry": { "attempts": 1, "sensors": 1 }
}