GHSA-5639-2j2p-m4mx: mako (CVE-2026-102991)

Package	Ecosystem	Affected	Fixed in
mako	PyPI	<1.4.2	1.4.2

Machine-written summary

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

Mako versions before 1.4.2 are vulnerable on Windows when a TemplateLookup URI begins with a drive designator such as C:/ or C:\, which bypasses the directory traversal check. An attacker who can influence template names or include paths passed to TemplateLookup.get_template() can read files outside the template directory, and may execute them if they contain Mako template syntax. Upgrade to Mako 1.4.2 or later.

Written 1 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
6.5	Medium	3.1	CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:L/A:N	CNA (GitHub_M)

CISA KEV Not listed.
EPSS 0.0036, the 29th percentile, on 8 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

Timeline

31 Oct 2026, 14:08 UTC First seen by agentprime
31 Oct 2026, 14:08 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.