CVE-2026-40611Lego: Arbitrary File Write via Path Traversal in Webroot HTTP-01 Provider
- 8.8HighCVSS base score
- 0.42%Exploitation in 30 daysEPSS · top 63% of all CVEs
- NoKnown exploitednot in CISA's KEV catalog
- YesPublic exploitsa reference or SSVC says so
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.
Public exploit
An exploit or proof of concept is public: anyone can try it against an unpatched system. A reference of the record is tagged as an exploit. CISA's SSVC rates its exploitation: a proof of concept is public.
Show the exploits1
References tagged exploit1 reference
- https://github.com/go-acme/lego/security/advisories/GHSA-qqx8-2xmm-jrv8 (opens in a new tab)x_refsource_CONFIRMexploit
Timeline
ID reserved
By GitHub_M
- 7 days later
· 7 days later
Published
- 3 months later
· 3 months later
Record updated
Changes after publication (a new score, a public exploit, EPSS crossing 1, 10 or 50 %, leaving KEV) are kept since November 2026; earlier ones are not known.
Scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| GitHub_MCNA (assigner) | 3.1 | High8.8 | CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H |
| redhat-SADPADP (enrichment) | 3.1 | High8.8 | CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H |
| NVDNVD · Deferred | 3.1 | High8.8 | CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H |
- EPSS (exploitation in 30 days)
- 0.42% · top 63% of all CVEs (15 Nov 2026)
- CISA SSVC
- Exploitation: poc · Automatable: no · Technical impact: total
The list uses the assigner's score when there is one, then CISA's, then NVD's: High 8.8.
Affected products
Affected packages
From reviewed advisories of the GitHub Advisory Database.
- Gogithub.com/go-acme/legoGHSA-qqx8-2xmm-jrv8 (opens in a new tab)
- Gogithub.com/go-acme/lego/v3GHSA-qqx8-2xmm-jrv8 (opens in a new tab)
- Gogithub.com/go-acme/lego/v4GHSA-qqx8-2xmm-jrv8 (opens in a new tab)
References
References5
- https://github.com/go-acme/lego/security/advisories/GHSA-qqx8-2xmm-jrv8 (opens in a new tab)x_refsource_CONFIRMexploit
- https://access.redhat.com/security/cve/CVE-2026-40611 (opens in a new tab)vdb-entryx_refsource_REDHAT
- RHBZ#2460233 (opens in a new tab)issue-trackingx_refsource_REDHAT
- https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-40611.json (opens in a new tab)x_sadp-csaf-vex
- https://access.redhat.com/errata/RHSA-2026:21772 (opens in a new tab)vendor-advisoryx_refsource_REDHAT
Sources
The same CVE in the primary databases and aggregators, to check against.
- CVE.org record (opens in a new tab)
- CVE List JSON (GitHub) (opens in a new tab)
- NVD (opens in a new tab)
- FIRST EPSS (opens in a new tab)
- EUVD EUVD-2026-24219 (opens in a new tab)
- OSV.dev (opens in a new tab)
- GitHub Advisory GHSA-qqx8-2xmm-jrv8 (opens in a new tab)
- CIRCL Vulnerability-Lookup (opens in a new tab)
Badge for a README or a ticket
[](https://cveledger.app/cve/CVE-2026-40611)Record last updated .