---
id: "CVE-2026-63660"
page: "https://infrastack.ai/live/CVE-2026-63660"
kind: "vulnerability"
aliases: ["CVE-2026-63660"]
title: "node-fontnik: crafted font causes heap overflow and process crash"
severity: "high"
cvss: 8.1
epss: null
exploited: false
status: "open"
category: "package"
products: []
ecosystems: []
tags: ["fonts", "maps", "node", "package", "self-hosted"]
not_affected_if: ["fonts-trusted-only", "not-installed"]
published_at: "2026-11-11T03:16:52+00:00"
first_seen_at: "2026-11-11T03:25:00+00:00"
updated_at: "2026-11-11T03:26:17+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-63660", "first_seen_at": "2026-11-11T03:25:00+00:00"}]
exploit_sources: []
---

# node-fontnik: crafted font causes heap overflow and process crash

Link for people: https://infrastack.ai/live/CVE-2026-63660 (this .md is for agents)

node-fontnik renders font glyphs as signed distance fields for map tools. A crafted font with an oversized glyph wraps a 32-bit allocation size, so the render writes past a too-small heap buffer, which can crash the process.

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

## How to check

- Check the installed version with `npm ls fontnik` in the project.
- Search the lockfile for `fontnik` to see every resolved version, including transitive copies.
- Note whether the service accepts uploaded or user-supplied fonts for glyph rendering.

## Fix

- node-fontnik: move to `0.7.7` or later.

## Timeline

- 2026-11-11T03:25:00+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-63660

## Documents

- [advisory] Vendor advisory: github.com https://github.com/mapbox/node-fontnik/security/advisories/GHSA-cfm6-c7rv-58xj
- [fix] Release notes: github.com https://github.com/mapbox/node-fontnik/releases/tag/v0.7.7

## From the sources

node-fontnik is a library that delivers a range of glyphs rendered as SDFs (signed distance fields) in a protocol buffer. Prior to version 0.7.7, a crafted font could trigger a heap out-of-bounds write in RenderSDF (include/mapbox/glyph_foundry_impl.hpp). RenderSDF computed the SDF bitmap allocation size as buffered_width * buffered_height in 32-bit unsigned int. Glyph dimensions are derived from the uploaded font's outline bounding box with no upper bound, so a glyph large enough to make that product exceed 2³² wrapped to a small value. The buffer was then under-allocated while the render loop still wrote one byte per pixel, corrupting the heap (CWE-190 → CWE-787) and crashing the process. A 680-byte font is enough to drive FreeType to a 65536×65536 buffered glyph, wrapping the size to 0. This issue has been patched in version 0.7.7.

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