Lego: Arbitrary File Write via Path Traversal in Webroot HTTP-01 Provider
Key facts
- Attack vector
- Network
- Privileges required
- None
- User interaction
- Required
- Attack complexity
- Low
- Impact type
- —
- Confidentiality · integrity · availability
- High · High · High
- Fix status
- Fixed
Attack profile from CVSS 3.1 · CNA. Fix status from CNA, GitHub and Red Hat.
Summary
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.
Why it matters now
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- Poc
- Automatable
- No
- Technical impact
- Total
The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| go-acme | lego | before 4.34.0 | 4.34.0 | Patch available | CNA |
| — | github.com/go-acme/lego/v4 (Go) | before 4.34.0 | 4.34.0 | Patch available | GHSA-qqx8-2xmm-jrv8 |
| — | github.com/go-acme/lego/v3 (Go) | up to 3.9.0 | — | No fix listed | GHSA-qqx8-2xmm-jrv8 |
| — | github.com/go-acme/lego (Go) | up to 2.7.2 | — | No fix listed | GHSA-qqx8-2xmm-jrv8 |
- lego Vendorgo-acme Affected before 4.34.0 Fixed in 4.34.0 Patch available CNA
- github.com/go-acme/lego/v4 (Go) Vendor— Affected before 4.34.0 Fixed in 4.34.0 Patch available GHSA-qqx8-2xmm-jrv8
- github.com/go-acme/lego/v3 (Go) Vendor— Affected up to 3.9.0 Fixed in — No fix listed GHSA-qqx8-2xmm-jrv8
- github.com/go-acme/lego (Go) Vendor— Affected up to 2.7.2 Fixed in — No fix listed GHSA-qqx8-2xmm-jrv8
Remediation
- Fix · CNA lego (go-acme) Fixed in 4.34.0
- Fix · GHSA-qqx8-2xmm-jrv8 github.com/go-acme/lego/v4 (Go) Fixed in 4.34.0 Advisory →
Red Hat 1 advisory
- RHSA-2026:21772 Released 2026-05-28 · Red Hat rating ImportantRed Hat OpenShift Dev Spaces 3.28.0 Release.
- Red Hat OpenShift Dev Spaces 3.28 registry.redhat.io/devspaces/code-rhel9, registry.redhat.io/devspaces/dashboard-rhel9, registry.redhat.io/devspaces/openvsx-rhel9 +3
Vendor assessments
Red Hat
Red Hat rating: Important. Red Hat's page for this CVE →
| Product | Status | Plan or fix |
|---|---|---|
| Red Hat OpenShift Dev Spaces 3.28 | Fixed | RHSA-2026:21772 |
Not affected: 1 product
- Red Hat OpenShift Dev Spaces 3.28
Timeline
- 2026-10-02 Threatist record created from CVE-2026-40611
- 2026-10-03 Alias added: GHSA-qqx8-2xmm-jrv8
References
More go-acme vulnerabilities
- TI-2025-34553 Lego does not enforce HTTPS CVSS 4.0LOW 2.3
Sources
- CVE-2026-40611 · CVE Program
- CVE-2026-40611 · NVD
- FIRST EPSS
- GHSA-qqx8-2xmm-jrv8 · GitHub Advisory Database · CC BY 4.0
- CVE-2026-40611 · Red Hat security data · CC BY 4.0
This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences