HighFix available
golang-github-xenolf-lego — security advisory
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.
- Products
- golang-github-xenolf-lego
- Affected versions
- 4.35.2-1, 4.35.2-2, 4.35.2-2~bpo13+1, 4.35.2-3, 4.35.2-3~bpo13+1, 4.9.1-1, 4.9.1-2, 4.9.1-3, 4.9.1-4
- Fixed versions
- 4.35.2-1
- CVEs
- CVE-2026-40611
- Confirmed fixed CVEs
- Not specified
- Updated in this feed
- 1 Nov 2026, 17:46 UTC · Revision 2
Source evidence
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.
osv:DEBIAN-CVE-2026-40611
golang-github-xenolf-lego
Fixed versions: Not specified
golang-github-xenolf-lego
Fixed versions: Not specified
golang-github-xenolf-lego
Fixed versions: 4.35.2-1
Complete source record
{
"id": "a8740960408d0d79deab8413d4b49490713084a9d0eaae5ad7ee7fb333bdd3eb",
"url": "https://osv.dev/vulnerability/DEBIAN-CVE-2026-40611",
"method": "structured",
"payload": {
"kind": "advisory",
"title": "DEBIAN-CVE-2026-40611",
"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.",
"evidence": "osv:DEBIAN-CVE-2026-40611",
"products": [
{
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"evidence": "/affected/0/package/name"
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"prerequisites": [],
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"affected_versions": [
{
"value": "4.35.2-1",
"evidence": "/affected/0/versions"
},
{
"value": "4.35.2-2",
"evidence": "/affected/0/versions"
},
{
"value": "4.35.2-2~bpo13+1",
"evidence": "/affected/0/versions"
},
{
"value": "4.35.2-3",
"evidence": "/affected/0/versions"
},
{
"value": "4.35.2-3~bpo13+1",
"evidence": "/affected/0/versions"
},
{
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"evidence": "/affected/0/versions"
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{
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{
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{
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{
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{
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],
"severity": "high",
"structured": {
"id": "DEBIAN-CVE-2026-40611",
"aliases": [
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"metrics": [
{
"type": "CVSS_V3",
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H"
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],
"affected": [
{
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"package": {
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"purl": "pkg:deb/debian/golang-github-xenolf-lego?arch=source&distro=bookworm",
"ecosystem": "Debian:12"
},
"versions": [
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"4.9.1-1",
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"database_specific": {
"source": "https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-40611.json"
},
"ecosystem_specific": {
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"ecosystem": "Debian:13"
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"versions": [
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"4.35.2-3~bpo13+1",
"4.9.1-2",
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"4.9.1-4"
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"database_specific": {
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{
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"package": {
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"purl": "pkg:deb/debian/golang-github-xenolf-lego?arch=source&distro=forky",
"ecosystem": "Debian:14"
},
"versions": [
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"4.9.1-3",
"4.9.1-4"
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},
"ecosystem_specific": {
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}
}
],
"modified": "2026-10-27T09:47:35.058543717Z",
"provider": "osv",
"upstream": [
"CVE-2026-40611"
],
"references": [
"https://security-tracker.debian.org/tracker/CVE-2026-40611"
]
},
"related_cves": [
{
"value": "CVE-2026-40611",
"evidence": "/upstream"
}
],
"security_relevant": true,
"severity_evidence": "/severity/0/score"
},
"source_id": "core-osv",
"document_id": 461181,
"published_at": "2026-04-21T18:16:52.457+00:00"
}