GHSA-6673-4983-2vx5: fonttools (CVE-2023-45139)

Package	Ecosystem	Affected	Fixed in
fonttools	PyPI	>=4.28.2, <4.43.0	4.43.0

Machine-written summary

Summary written by Claude Haiku from the source advisory. Not reviewed by a person.

The fonttools PyPI package versions 4.28.2 up to but not including 4.43.0 are vulnerable to XML External Entity Injection when the subsetting module parses an OT-SVG font containing an SVG table. An attacker who can supply a crafted font for subsetting can read arbitrary files from the host filesystem or make web requests from it. Upgrade to fonttools 4.43.0 or later.

Written 5 Nov 2026.

Not analysed yet

We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.

Severity and exploitation

Score	Rating	CVSS	Vector	Source
7.5	High	3.1	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N	CNA (GitHub_M)

CISA KEV Not listed.
EPSS 0.012, the 69th percentile, on 10 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

Timeline

31 Oct 2026, 14:36 UTC First seen by agentprime
31 Oct 2026, 14:36 UTC Confirmed by OSV

Sources

Facts on this page come from the GitHub Advisory Database (CC-BY 4.0), OSV and the other sources listed, as published. We don’t reproduce full advisory descriptions, which can contain exploit code.