CVE-2026-40611

unknown

Published 2026-04-16 · Modified 2026-05-05

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CVSS v3

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CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

CVSS v4 NEW

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not yet in upstream

VIR risk

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Description

Let's Encrypt client and ACME library written in Go (Lego). Prior to 4.34.0, the webroot HTTP-01 challenge provider in lego is vulnerable to arbitrary file write and deletion via path traversal. A malicious ACME server can supply a crafted challenge token containing ../ sequences, causing lego to write attacker-influenced content to any path writable by the lego process. This vulnerability is fixed in 4.34.0.

Predictions

Exploit likelihood

30%

Patch ETA

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Heuristic predictions, AS-IS, for prioritization only.

Mitigations

No mitigations published for this CVE yet.

The vendor-content worker queues fetches as references arrive (check back in a few minutes). Or — if you've already worked around this in production — publish your fix to the community-verified tier.

✚ Propose a mitigation on Community → Mitigations published via the community go through AI scoring + 2 human reviewers + 7-day silent objection window before landing here with source_tier=community-verified.

OS impact

OS	Version	Status
debian	bookworm	affected
debian	bullseye	affected
debian	forky	affected
debian	sid	affected
debian	trixie	affected

Package impact

Ecosystem	Package	Vulnerable	Fixed
Go	github.com/go-acme/lego/v4	`<4.34.0`	`4.34.0`
Go	github.com/go-acme/lego/v3	`<=3.9.0`
Go	github.com/go-acme/lego	`<=2.7.2`

References

Community-verified mitigations for this CVE will appear above when contributors publish them.

Verify integrity in audit chain (admin only). AS-IS.