{"cve":"CVE-2026-40611","nvd":{"published":"2026-04-21T18:16:52.457","modified":"2026-10-26T21:10:00.170","status":"Deferred","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.","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H","score":8.8},"cwes":["CWE-22"],"references":["https://github.com/go-acme/lego/security/advisories/GHSA-qqx8-2xmm-jrv8","https://access.redhat.com/errata/RHSA-2026:21772","https://access.redhat.com/security/cve/CVE-2026-40611","https://bugzilla.redhat.com/show_bug.cgi?id=2460233","https://github.com/go-acme/lego/security/advisories/GHSA-qqx8-2xmm-jrv8"],"products":[],"source":"nvd","synced_at":"2026-10-26T21:38:48.864438205+00:00"},"epss":{"cve":"CVE-2026-40611","score":0.0034,"percentile":0.27198,"date":"2026-10-26"},"kev":null,"osv":[{"id":"GHSA-qqx8-2xmm-jrv8","url":"https://osv.dev/vulnerability/GHSA-qqx8-2xmm-jrv8","summary":"ACME Lego: Arbitrary File Write via Path Traversal in Webroot HTTP-01 Provider","modified":"2026-09-10T03:51:02.915079211Z","packages":[{"ecosystem":"Go","name":"github.com/go-acme/lego/v4","purl":"pkg:golang/github.com/go-acme/lego/v4","ranges":["<4.34.0"],"fixed":["4.34.0"]},{"ecosystem":"Go","name":"github.com/go-acme/lego/v3","purl":"pkg:golang/github.com/go-acme/lego/v3","ranges":["<=3.9.0"],"fixed":[]},{"ecosystem":"Go","name":"github.com/go-acme/lego","purl":"pkg:golang/github.com/go-acme/lego","ranges":["<=2.7.2"],"fixed":[]}]},{"id":"GO-2026-5593","url":"https://osv.dev/vulnerability/GO-2026-5593","summary":"ACME Lego: Arbitrary File Write via Path Traversal in Webroot HTTP-01 Provider in github.com/go-acme/lego","modified":"2026-07-24T19:00:24.441014176Z","packages":[{"ecosystem":"Go","name":"github.com/go-acme/lego/v4","purl":"pkg:golang/github.com/go-acme/lego/v4","ranges":["<4.34.0"],"fixed":["4.34.0"]}]}],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}