# [CRIT] [GHSA / CRITICAL] CVE-2026-53633: Vitest Browser: Exposed Browser Mode API Can Proxy CDP and Overwrite Config Files, Leading to RCE

**Source:** GitHub Security Advisories
**Published:** 2026-06-15
**Article:** https://github.com/advisories/GHSA-g8mr-85jm-7xhm

## Threat Profile

Vitest Browser: Exposed Browser Mode API Can Proxy CDP and Overwrite Config Files, Leading to RCE

## Summary

Vitest Browser Mode exposes a `cdp()` API that forwards raw Chrome DevTools Protocol (CDP) methods over the Vitest browser WebSocket RPC. CDP is not gated by `browser.api.allowWrite`, `browser.api.allowExec`, `api.allowWrite`, or `api.allowExec`.

As a result, disabling Browser Mode write and exec operations does not prevent a browser API client from using CDP to perform equivalent acti…

## Indicators of Compromise (high-fidelity only)

- **CVE:** `CVE-2026-53633`

## MITRE ATT&CK Techniques

- **T1539** — Steal Web Session Cookie
- **T1555.003** — Credentials from Web Browsers
- **T1190** — Exploit Public-Facing Application
- **T1204.002** — User Execution: Malicious File
- **T1562.001** — Impair Defenses: Disable or Modify Tools
- **T1546** — Event Triggered Execution
- **T1059.007** — Command and Scripting Interpreter: JavaScript
- **T1059** — Command and Scripting Interpreter

## Kill chain phases observed

_(none detected from narrative keywords)_

## Recommended hunts

### Vitest Browser API listening on all interfaces (CVE-2026-53633 pre-condition)

`UC_54_3` · phase: **weapon** · confidence: **High** · AI-generated for this article

**Splunk SPL (CIM):**
```spl
| tstats `summariesonly` count min(_time) as firstTime max(_time) as lastTime from datamodel=Endpoint.Processes where Processes.process_name="node.exe" Processes.process="*vitest*" Processes.process="*browser.api.host*" Processes.process="*0.0.0.0*" by Processes.dest Processes.user Processes.process Processes.parent_process_name | `drop_dm_object_name(Processes)` | convert ctime(firstTime) ctime(lastTime)
```

**Defender KQL:**
```kql
DeviceProcessEvents
| where Timestamp > ago(7d)
| where FileName =~ "node.exe" or InitiatingProcessFileName =~ "node.exe"
| where ProcessCommandLine has_any ("vitest","@vitest/browser","vite-plus")
| where ProcessCommandLine has "browser.api.host" and ProcessCommandLine has "0.0.0.0"
| where AccountName !endswith "$"
| project Timestamp, DeviceName, AccountName, FileName, ProcessCommandLine, InitiatingProcessFileName, InitiatingProcessCommandLine, FolderPath
| order by Timestamp desc
```

### Inbound non-loopback connection to Vitest browser API listener (TCP/63315)

`UC_54_4` · phase: **delivery** · confidence: **High** · AI-generated for this article

**Splunk SPL (CIM):**
```spl
| tstats `summariesonly` count min(_time) as firstTime max(_time) as lastTime values(All_Traffic.src) as src_ips from datamodel=Network_Traffic.All_Traffic where All_Traffic.dest_port=63315 All_Traffic.transport=tcp by All_Traffic.dest All_Traffic.app | `drop_dm_object_name(All_Traffic)` | iplocation src_ips | where NOT cidrmatch("127.0.0.0/8", src_ips) AND NOT cidrmatch("::1/128", src_ips)
```

**Defender KQL:**
```kql
DeviceNetworkEvents
| where Timestamp > ago(7d)
| where ActionType in ("InboundConnectionAccepted","ListeningConnectionCreated","ConnectionAccepted")
| where LocalPort == 63315
| where InitiatingProcessFileName =~ "node.exe"
| where InitiatingProcessCommandLine has_any ("vitest","@vitest/browser","vite-plus")
| where RemoteIPType != "Loopback" and RemoteIP !startswith "169.254"
| project Timestamp, DeviceName, LocalIP, LocalPort, RemoteIP, RemoteIPType, RemotePort, InitiatingProcessFileName, InitiatingProcessCommandLine, InitiatingProcessAccountName
| order by Timestamp desc
```

### Vitest false-sense-of-security config: allowWrite/allowExec false but CDP bridge exposed

`UC_54_5` · phase: **weapon** · confidence: **High** · AI-generated for this article

**Splunk SPL (CIM):**
```spl
| tstats `summariesonly` count min(_time) as firstTime max(_time) as lastTime from datamodel=Endpoint.Processes where Processes.process_name="node.exe" Processes.process="*vitest*" Processes.process="*allowWrite*" Processes.process="*allowExec*" by Processes.dest Processes.user Processes.process Processes.parent_process_name | `drop_dm_object_name(Processes)` | regex process="(?i)allowWrite\s*[:=]\s*false" | regex process="(?i)allowExec\s*[:=]\s*false" | regex process="(?i)(browser\.api\.host|--host)[\s=]+(0\.0\.0\.0|::|[^\s]+)"
```

**Defender KQL:**
```kql
DeviceProcessEvents
| where Timestamp > ago(7d)
| where FileName =~ "node.exe" or InitiatingProcessFileName =~ "node.exe"
| where ProcessCommandLine has_any ("vitest","@vitest/browser","vite-plus")
| where ProcessCommandLine matches regex @"(?i)allowWrite\s*[:=]\s*false"
| where ProcessCommandLine matches regex @"(?i)allowExec\s*[:=]\s*false"
| where ProcessCommandLine has "browser.api.host" and ProcessCommandLine has_any ("0.0.0.0","::")
| where not(ProcessCommandLine matches regex @"(?i)allowCDP\s*[:=]\s*false")
| where AccountName !endswith "$"
| project Timestamp, DeviceName, AccountName, FileName, ProcessCommandLine, InitiatingProcessFileName, FolderPath
| order by Timestamp desc
```

### vite/vitest config file modified by browser-context process (CVE-2026-53633 payload drop)

`UC_54_6` · phase: **install** · confidence: **High** · AI-generated for this article

**Splunk SPL (CIM):**
```spl
| tstats `summariesonly` count min(_time) as firstTime max(_time) as lastTime from datamodel=Endpoint.Filesystem where Filesystem.action IN ("created","modified","renamed") (Filesystem.file_name="vite.config.ts" OR Filesystem.file_name="vite.config.js" OR Filesystem.file_name="vite.config.mjs" OR Filesystem.file_name="vite.config.cjs" OR Filesystem.file_name="vitest.config.ts" OR Filesystem.file_name="vitest.config.js" OR Filesystem.file_name="vitest.config.mjs" OR Filesystem.file_name="vitest.config.cjs") (Filesystem.process_name="chrome.exe" OR Filesystem.process_name="chromium.exe" OR Filesystem.process_name="msedge.exe" OR Filesystem.process_name="msedgewebview2.exe" OR Filesystem.process_name="firefox.exe" OR Filesystem.process_name="brave.exe" OR Filesystem.process_name="headless_shell.exe" OR Filesystem.process_name="playwright.exe") by Filesystem.dest Filesystem.user Filesystem.file_name Filesystem.file_path Filesystem.process_name | `drop_dm_object_name(Filesystem)`
```

**Defender KQL:**
```kql
DeviceFileEvents
| where Timestamp > ago(7d)
| where ActionType in ("FileCreated","FileModified","FileRenamed")
| where FileName matches regex @"(?i)^(vite|vitest)\.config\.(ts|js|mjs|cjs)$"
| where InitiatingProcessFileName has_any ("chrome.exe","chromium.exe","msedge.exe","msedgewebview2.exe","firefox.exe","brave.exe","headless_shell.exe","playwright.exe","opera.exe")
| project Timestamp, DeviceName, FileName, FolderPath, PreviousFileName, PreviousFolderPath, SHA256, InitiatingProcessFileName, InitiatingProcessParentFileName, InitiatingProcessCommandLine, InitiatingProcessAccountName, FileOriginUrl
| order by Timestamp desc
```

### WebSocket access to Vitest browser API tester endpoint (CVE-2026-53633 exploit signature)

`UC_54_7` · phase: **exploit** · confidence: **High** · AI-generated for this article

**Splunk SPL (CIM):**
```spl
| tstats `summariesonly` count values(Web.user) as users values(Web.src) as src_ip values(Web.dest) as dest_ip from datamodel=Web where (Web.url="*__vitest_browser_api__*" OR Web.url="*__vitest_test__*") by Web.src Web.dest Web.url Web.http_user_agent _time | `drop_dm_object_name(Web)` | search url="*type=tester*" OR url="*sendCdpEvent*" OR url="*__vitest_test__*"
```

**Defender KQL:**
```kql
DeviceNetworkEvents
| where Timestamp > ago(7d)
| where isnotempty(RemoteUrl)
| where RemoteUrl has_any ("__vitest_browser_api__","__vitest_test__")
   or (RemotePort == 63315 and RemoteUrl has "type=tester")
| project Timestamp, DeviceName, InitiatingProcessFileName, InitiatingProcessCommandLine, RemoteIP, RemotePort, RemoteUrl, InitiatingProcessAccountName
| order by Timestamp desc
```

### Config-reload RCE: node.exe spawns shell/LOLBin within 30s of vite/vitest config write

`UC_54_8` · phase: **exploit** · confidence: **High** · AI-generated for this article

**Splunk SPL (CIM):**
```spl
| tstats `summariesonly` min(_time) as fileTime values(Filesystem.process_name) as writer from datamodel=Endpoint.Filesystem where Filesystem.action IN ("created","modified") (Filesystem.file_name="vite.config.ts" OR Filesystem.file_name="vite.config.js" OR Filesystem.file_name="vite.config.mjs" OR Filesystem.file_name="vite.config.cjs" OR Filesystem.file_name="vitest.config.ts" OR Filesystem.file_name="vitest.config.js" OR Filesystem.file_name="vitest.config.mjs") by Filesystem.dest Filesystem.file_name Filesystem.file_path | `drop_dm_object_name(Filesystem)` | join type=inner dest [ | tstats `summariesonly` min(_time) as procTime values(Processes.process) as childCmd from datamodel=Endpoint.Processes where Processes.parent_process_name="node.exe" (Processes.process_name="cmd.exe" OR Processes.process_name="powershell.exe" OR Processes.process_name="pwsh.exe" OR Processes.process_name="wscript.exe" OR Processes.process_name="cscript.exe" OR Processes.process_name="mshta.exe" OR Processes.process_name="bash.exe" OR Processes.process_name="sh.exe" OR Processes.process_name="wmic.exe" OR Processes.process_name="curl.exe" OR Processes.process_name="wget.exe" OR Processes.process_name="bitsadmin.exe" OR Processes.process_name="certutil.exe" OR Processes.process_name="rundll32.exe" OR Processes.process_name="regsvr32.exe") by Processes.dest Processes.process_name Processes.process Processes.parent_process_name | `drop_dm_object_name(Processes)` ] | where procTime >= fileTime AND procTime <= fileTime + 30 | eval delaySec = procTime - fileTime | table fileTime procTime delaySec dest file_name file_path writer process_name childCmd
```

**Defender KQL:**
```kql
let WindowSeconds = 30;
let ConfigWrites = DeviceFileEvents
    | where Timestamp > ago(7d)
    | where ActionType in ("FileCreated","FileModified","FileRenamed")
    | where FileName matches regex @"(?i)^(vite|vitest)\.config\.(ts|js|mjs|cjs)$"
    | project ConfigWriteTime = Timestamp, DeviceId, DeviceName, ConfigPath = FolderPath, ConfigFile = FileName, ConfigWriter = InitiatingProcessFileName, WriterCmd = InitiatingProcessCommandLine;
ConfigWrites
| join kind=inner (
    DeviceProcessEvents
    | where Timestamp > ago(7d)
    | where InitiatingProcessFileName =~ "node.exe"
    | where InitiatingProcessCommandLine has_any ("vitest","@vitest/browser","vite")
    | where FileName in~ ("cmd.exe","powershell.exe","pwsh.exe","wscript.exe","cscript.exe","mshta.exe","bash.exe","sh.exe","wmic.exe","curl.exe","wget.exe","bitsadmin.exe","certutil.exe","rundll32.exe","regsvr32.exe","net.exe","netsh.exe")
    | project ChildSpawnTime = Timestamp, DeviceId, ChildProcess = FileName, ChildCmd = ProcessCommandLine, NodeCmd = InitiatingProcessCommandLine, NodeFolderPath = InitiatingProcessFolderPath, AccountName
) on DeviceId
| where ChildSpawnTime between (ConfigWriteTime .. ConfigWriteTime + WindowSeconds * 1s)
| extend DelaySec = datetime_diff('second', ChildSpawnTime, ConfigWriteTime)
| project ConfigWriteTime, ChildSpawnTime, DelaySec, DeviceName, AccountName, ConfigPath, ConfigFile, ConfigWriter, WriterCmd, ChildProcess, ChildCmd, NodeCmd
| order by ConfigWriteTime desc
```

### Infostealer — non-browser process accessing browser cookie/login DBs

`UC_BROWSER_STEALER` · phase: **actions** · confidence: **High**

**Splunk SPL (CIM):**
```spl
| tstats `summariesonly` count min(_time) as firstTime max(_time) as lastTime
    from datamodel=Endpoint.Filesystem
    where (Filesystem.file_path="*\Google\Chrome\User Data\*\Login Data*"
        OR Filesystem.file_path="*\Google\Chrome\User Data\*\Cookies*"
        OR Filesystem.file_path="*\Microsoft\Edge\User Data\*\Login Data*"
        OR Filesystem.file_path="*\Mozilla\Firefox\Profiles\*\logins.json*"
        OR Filesystem.file_path="*\Mozilla\Firefox\Profiles\*\cookies.sqlite*")
      AND NOT Filesystem.process_name IN ("chrome.exe","msedge.exe","firefox.exe","brave.exe","opera.exe")
    by Filesystem.dest, Filesystem.process_name, Filesystem.file_path, Filesystem.user
| `drop_dm_object_name(Filesystem)`
```

**Defender KQL:**
```kql
DeviceFileEvents
| where Timestamp > ago(7d)
| where InitiatingProcessAccountName !endswith "$"
| where FolderPath has_any (@"\Google\Chrome\User Data\", @"\Microsoft\Edge\User Data\", @"\Mozilla\Firefox\Profiles\")
| where FileName in~ ("Login Data","Cookies","logins.json","cookies.sqlite")
| where InitiatingProcessFileName !in~ ("chrome.exe","msedge.exe","firefox.exe","brave.exe","opera.exe")
| project Timestamp, DeviceName, InitiatingProcessAccountName, InitiatingProcessFileName, FolderPath, FileName, ActionType
```

### Article-specific behavioural hunt — [GHSA / CRITICAL] CVE-2026-53633: Vitest Browser: Exposed Browser Mode API Can P

`UC_54_2` · phase: **exploit** · confidence: **High**

**Splunk SPL (CIM):**
```spl
``` Article-specific bespoke detection — [GHSA / CRITICAL] CVE-2026-53633: Vitest Browser: Exposed Browser Mode API Can P ```
| tstats `summariesonly` count earliest(_time) AS firstTime latest(_time) AS lastTime
    from datamodel=Endpoint.Processes
    where (Processes.process_name IN ("node.js"))
    by Processes.dest, Processes.user, Processes.process_name,
       Processes.process, Processes.parent_process_name, Processes.process_path
| `drop_dm_object_name(Processes)`
| `security_content_ctime(firstTime)`
| append [
| tstats `summariesonly` count
    from datamodel=Endpoint.Filesystem
    where Filesystem.action IN ("created","modified")
      AND (Filesystem.file_name IN ("node.js"))
    by Filesystem.dest, Filesystem.user, Filesystem.process_name,
       Filesystem.file_path, Filesystem.file_name
| `drop_dm_object_name(Filesystem)`
]
```

**Defender KQL:**
```kql
// Article-specific bespoke detection — [GHSA / CRITICAL] CVE-2026-53633: Vitest Browser: Exposed Browser Mode API Can P
// Hunts the actual binaries / paths / commandline fragments named
// in the article instead of a generic technique-class template.
DeviceProcessEvents
| where Timestamp > ago(30d)
| where (FileName in~ ("node.js"))
| project Timestamp, DeviceName, AccountName, FileName,
          FolderPath, ProcessCommandLine,
          InitiatingProcessFileName, InitiatingProcessCommandLine
| order by Timestamp desc

// File-creation events for the named binaries / paths
DeviceFileEvents
| where Timestamp > ago(30d)
| where ActionType in ("FileCreated","FileModified")
| where (FileName in~ ("node.js"))
| project Timestamp, DeviceName, AccountName, FolderPath,
          FileName, ActionType, InitiatingProcessFileName,
          InitiatingProcessCommandLine
| order by Timestamp desc
```

### IOC-driven hunts (use shared templates)

These are standard IOC-substitution hunts — the canonical SPL and KQL live once in [`_TEMPLATES.md`](../_TEMPLATES.md), so we don't repeat the same boilerplate on every CVE / hash / network-IOC briefing.

- **Asset exposure — vulnerability matches article CVE(s)** ([template](../_TEMPLATES.md#asset-exposure)) — phase: **recon**, confidence: **High**
  - CVE(s): `CVE-2026-53633`


## Why this matters

Severity classified as **CRIT** based on: CVE present, 9 use case(s) fired, 8 technique(s) inferred. Read the full article for actor attribution, tooling details, and any defanged IOCs in the body that aren't visible in the RSS summary.