{"id":"CVE-2026-40611","aliases":["GHSA-qqx8-2xmm-jrv8","GO-2026-5593"],"url":"https://o3.security/vulnerability/CVE-2026-40611","summary":"Lego: Arbitrary File Write via Path Traversal in Webroot HTTP-01 Provider","details":"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.","published":"2026-04-21T17:58:35.221Z","modified":"2026-08-07T11:31:34.454321783Z","cvss":{"score":8.8,"severity":"HIGH","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H"},"epss":{"score":0.0034,"percentile":0.26631,"asOf":"2026-08-08"},"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"Go","name":"github.com/go-acme/lego/v4","fixedVersion":"4.34.0"},{"ecosystem":"Go","name":"github.com/go-acme/lego/v3","fixedVersion":null},{"ecosystem":"Go","name":"github.com/go-acme/lego","fixedVersion":null}],"fix":null,"references":[{"type":"WEB","url":"https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-40611.json"},{"type":"ADVISORY","url":"https://access.redhat.com/errata/RHSA-2026:21772"},{"type":"ADVISORY","url":"https://access.redhat.com/security/cve/CVE-2026-40611"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/40xxx/CVE-2026-40611.json"},{"type":"ADVISORY","url":"https://github.com/go-acme/lego/security/advisories/GHSA-qqx8-2xmm-jrv8"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-40611"},{"type":"REPORT","url":"https://bugzilla.redhat.com/show_bug.cgi?id=2460233"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-07T11:31:34.454321783Z"}}