{"id":"UBUNTU-CVE-2026-40611","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.","modified":"2026-06-30T18:18:03.338604103Z","published":"2026-04-21T18:16:00Z","upstream":["CVE-2026-40611"],"references":[{"type":"REPORT","url":"https://ubuntu.com/security/CVE-2026-40611"},{"type":"REPORT","url":"https://www.cve.org/CVERecord?id=CVE-2026-40611"},{"type":"REPORT","url":"https://github.com/go-acme/lego/security/advisories/GHSA-qqx8-2xmm-jrv8"}],"affected":[{"package":{"name":"golang-github-xenolf-lego","ecosystem":"Ubuntu:18.04:LTS","purl":"pkg:deb/ubuntu/golang-github-xenolf-lego?arch=source&distro=bionic"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["0.3.1-5"],"ecosystem_specific":{"binaries":[{"binary_name":"golang-github-xenolf-lego-dev","binary_version":"0.3.1-5"},{"binary_name":"lego","binary_version":"0.3.1-5"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-40611.json"}},{"package":{"name":"golang-github-xenolf-lego","ecosystem":"Ubuntu:20.04:LTS","purl":"pkg:deb/ubuntu/golang-github-xenolf-lego?arch=source&distro=focal"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["0.3.1-5","2.7.2+dfsg-1","3.2.0-1"],"ecosystem_specific":{"binaries":[{"binary_name":"golang-github-xenolf-lego-dev","binary_version":"3.2.0-1"},{"binary_name":"lego","binary_version":"3.2.0-1"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-40611.json"}},{"package":{"name":"golang-github-xenolf-lego","ecosystem":"Ubuntu:22.04:LTS","purl":"pkg:deb/ubuntu/golang-github-xenolf-lego?arch=source&distro=jammy"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["3.2.0-3.1","4.1.3-3ubuntu1","4.1.3-3ubuntu1.22.04.1"],"ecosystem_specific":{"binaries":[{"binary_name":"golang-github-xenolf-lego-dev","binary_version":"4.1.3-3ubuntu1.22.04.1"},{"binary_name":"lego","binary_version":"4.1.3-3ubuntu1.22.04.1"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-40611.json"}},{"package":{"name":"golang-github-xenolf-lego","ecosystem":"Ubuntu:Pro:24.04:LTS","purl":"pkg:deb/ubuntu/golang-github-xenolf-lego?arch=source&distro=esm-apps%2Fnoble"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["4.9.1-1build1","4.9.1-2","4.9.1-2ubuntu0.24.04.1","4.9.1-2ubuntu0.24.04.2","4.9.1-2ubuntu0.24.04.2+esm1","4.9.1-2ubuntu0.24.04.3","4.9.1-2ubuntu0.24.04.3+esm1","4.9.1-2ubuntu0.24.04.3+esm2"],"ecosystem_specific":{"binaries":[{"binary_version":"4.9.1-2ubuntu0.24.04.3+esm2","binary_name":"golang-github-xenolf-lego-dev"},{"binary_name":"lego","binary_version":"4.9.1-2ubuntu0.24.04.3+esm2"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-40611.json"}},{"package":{"name":"golang-github-xenolf-lego","ecosystem":"Ubuntu:25.10","purl":"pkg:deb/ubuntu/golang-github-xenolf-lego?arch=source&distro=questing"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["4.9.1-2"],"ecosystem_specific":{"binaries":[{"binary_version":"4.9.1-2","binary_name":"golang-github-xenolf-lego-dev"},{"binary_name":"lego","binary_version":"4.9.1-2"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-40611.json"}},{"package":{"name":"golang-github-xenolf-lego","ecosystem":"Ubuntu:26.04:LTS","purl":"pkg:deb/ubuntu/golang-github-xenolf-lego?arch=source&distro=resolute"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["4.9.1-2","4.9.1-3","4.9.1-4"],"ecosystem_specific":{"binaries":[{"binary_name":"golang-github-xenolf-lego-dev","binary_version":"4.9.1-4"},{"binary_version":"4.9.1-4","binary_name":"lego"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-40611.json"}}],"schema_version":"1.7.5","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H"},{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H"},{"type":"Ubuntu","score":"medium"}]}