---
id: "CVE-2026-97371"
kind: "vulnerability"
aliases: ["CVE-2026-97371"]
title: "ntopng: custom-category packet matching corrupts the stack, crashing the monitor"
severity: "medium"
cvss: 5.3
epss: null
exploited: false
status: "open"
category: "package"
products: []
ecosystems: []
tags: ["network-monitoring", "ntopng", "package", "self-hosted"]
not_affected_if: ["fixed-version", "no-custom-categories"]
published_at: "2026-11-05T17:18:22+00:00"
first_seen_at: "2026-11-05T17:40:05+00:00"
updated_at: "2026-11-05T17:42:37+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-97371", "first_seen_at": "2026-11-05T17:40:05+00:00"}]
exploit_sources: []
---

# ntopng: custom-category packet matching corrupts the stack, crashing the monitor

ntopng writes a four-byte protocol-category value into a two-byte variable on the stack when it dissects packets that match custom-category rules. A remote, unauthenticated attacker on a monitored network segment can send such packets and corrupt the stack, causing a denial of service.

_Summary, check and fix written by a model from the sources; labelled as such._

## How to check

- Check the installed ntopng version with `ntopng --version` and compare it with the fixed version below.
- Check whether custom categories are configured in ntopng, since only packets matching those rules reach the flawed code path.

## Fix

- ntopng: `6.7.260721`

## Timeline

- 2026-11-05T17:40:05+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-97371

## Documents

- [advisory] Vendor advisory: github.com https://github.com/ntop/ntopng/security/advisories/GHSA-26jm-9qfw-89w7
- [fix] Patch: github.com https://github.com/ntop/ntopng/commit/96acb6187950a6a49ca827e49973c3e0c27ea664

## From the sources

ntopng is a web-based network traffic monitoring application. Prior to 6.7.260721, ndpi_get_custom_category_match writes a four-byte nDPI protocol-category value through a pointer to the two-byte id variable in IpAddress::reloadBlacklist in src/IpAddress.cpp during packet dissection and host initialization. A remote unauthenticated attacker on a monitored network segment can send packets that match custom-category rules, causing stack corruption and denial of service without user interaction. This issue is fixed in version 6.7.260721.

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