---
title: "WEB-APA-009 Apache ETag Reveals Inode Numbers"
canonical: https://openvapt.com/checks/WEB-APA-009.html
html: https://openvapt.com/checks/WEB-APA-009.html
site: OpenVAPT, https://openvapt.com/
license: OpenVAPT Source-Available Licence 1.3, https://openvapt.com/legal/licence-text.html
modified: 2026-10-14
version: 0.1.0-alpha.6
---

# WEB-APA-009 Apache ETag Reveals Inode Numbers

FileETag includes INode (or All), so ETag headers leak filesystem inode numbers of served files.

- Domain: Web Apps
- Severity: Low
- Control category: Information Exposure
- Fix effort: low
- CVSS v3.1 vector: `CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N`
- CIS Controls v8: 16.7
- NIST CSF 2.0: PR.PS-01
- CWE: CWE-497
- OWASP Top 10 2021: A05:2021
- OWASP ASVS 4.0.3: 14.3.3
- OWASP WSTG v4.2: WSTG-INFO-02
- NIST SP 800-53 Rev. 5: SI-11, CM-6
- Benchmark topic: Web server information disclosure in headers (topic only, no benchmark text)

## Why It Matters

Inode numbers help distinguish servers behind a load balancer and have been used to infer file identity across hosts (CVE-2003-1418). The Apache 2.4 default of MTime Size does not include them.

## How It Detects

Reads every FileETag directive and flags values containing INode or All.

## How to Fix

Set  FileETag MTime Size  or  FileETag None  and reload.

## How to Verify

```
curl -sI https://<site>/robots.txt | grep -i etag  should show a two-part value, not three.
```

## Learn the Theory

- [P18 Web Server Hardening: nginx and Apache](https://openvapt.com/academy/p18.md)

## References

- [Apache HTTP Server, FileETag directive](https://httpd.apache.org/docs/2.4/mod/core.html#fileetag)
- [CVE-2003-1418, Apache inode disclosure in ETag](https://www.cve.org/CVERecord?id=CVE-2003-1418)

## Source Code

https://github.com/OpenVAPT/openvapt/blob/574f7f3333c44b75a3c649e2d93a76d507f75adf/internal/checks/web/serverconf.go

Run it: `openvapt scan --only WEB-APA-009`. Read it offline: `openvapt explain WEB-APA-009`.

---

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