CVE-2026-40611

HIGHPre-NVD 8.88.8—
EchelonGraph scoreMEDIUM confidence

This high-severity CVE scores 8.8 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.3%, top 73% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: epss, secondary
Elevated
8.8EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 8.8Exploit: Elevated riskExposed: 0

A fix is available — apply it.

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 v3
8.8
EG Score
8.8(medium)
EG Risk
56(Track*)
EG Risk 56/100SSVC: Track*

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity88% × 45%
Exploitation40% × 40%
Automatability0% × 15%
Action: Watch closely — could escalate to Attend.
EPSS PROB
0%
EPSS %ILE
27%
KEV
Not listed

Published

April 21, 2026

Last Modified

July 15, 2026

Advisory Details (1)

Auto-updated May 2, 2026
🔬 Proof of concept available. Patch available. Sources: github.
github Patch Available🟡 PoC Available

Arbitrary File Write via Path Traversal in Webroot HTTP-01 Provider · Advisory · go-acme/lego · GitHub

https://github.com/go-acme/lego/security/advisories/GHSA-qqx8-2xmm-jrv8

Vendor Advisories for CVE-2026-40611(1)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Patch Availability(1)

Vendor / EcosystemFixed in / PatchReleasedSource
redhatdevspaces/traefik-rhel9:17797867792026-05-28redhat

Patches are aggregated from vendor advisories (Red Hat, Microsoft, Cisco, GitHub) and package ecosystems (OSV, GHSA). Multiple rows for the same upstream release have been deduplicated.

Affected Packages

(7 across 5 ecosystems)
Go(3)
PackageVulnerable rangeFixed inDependents
github.com/go-acme/lego———
github.com/go-acme/lego/v3———
github.com/go-acme/lego/v4—4.34.0—
Debian:11(1)
PackageVulnerable rangeFixed inDependents
golang-github-xenolf-lego3.2.0-3.1 ... 4.9.1-4 (15 versions)——
Debian:12(1)
PackageVulnerable rangeFixed inDependents
golang-github-xenolf-lego4.35.2-1 ... 4.9.1-4 (9 versions)——
Debian:13(1)
PackageVulnerable rangeFixed inDependents
golang-github-xenolf-lego4.35.2-1 ... 4.9.1-4 (8 versions)——
Debian:14(1)
PackageVulnerable rangeFixed inDependents
golang-github-xenolf-lego4.9.1-2, 4.9.1-3, 4.9.1-44.35.2-1—

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 5× in last 7d / 56× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

Showing the most recent 100 of 171 total refreshes for this CVE.

  1. 2026-08-26 14:46 UTCEPSS rescore
  2. 2026-08-25 13:49 UTCEPSS rescore
  3. 2026-08-23 00:19 UTCEPSS rescore
  4. 2026-08-21 23:49 UTCEPSS rescore
  5. 2026-08-20 22:55 UTCEPSS rescore
  6. 2026-08-19 17:03 UTCEPSS rescore
  7. 2026-08-18 13:48 UTCEPSS rescore
  8. 2026-08-17 13:47 UTCEPSS rescore
  9. 2026-08-16 14:56 UTCEPSS rescore
  10. 2026-08-16 06:17 UTCEG score recompute
  11. 2026-08-16 06:17 UTCVendor advisory
  12. 2026-08-16 02:14 UTCEPSS rescore
  13. 2026-08-15 01:30 UTCEPSS rescore
  14. 2026-08-14 18:04 UTCVendor advisory
  15. 2026-08-14 04:28 UTCEG score recompute
  16. 2026-08-14 04:28 UTCVendor advisory
  17. 2026-08-13 22:00 UTCEPSS rescore
  18. 2026-08-13 08:44 UTCVendor advisory
  19. 2026-08-12 18:39 UTCEG score recompute
  20. 2026-08-12 18:39 UTCVendor advisory
  21. 2026-08-12 13:51 UTCEPSS rescore
  22. 2026-08-11 16:51 UTCEG score recompute
  23. 2026-08-11 16:51 UTCVendor advisory
  24. 2026-08-11 13:43 UTCEPSS rescore
  25. 2026-08-11 02:26 UTCEG score recompute
Show 75 more
  1. 2026-08-11 02:26 UTCVendor advisory
  2. 2026-08-11 00:00 UTCEPSS rescore
  3. 2026-08-10 05:25 UTCVendor advisory
  4. 2026-08-09 16:33 UTCEG score recompute
  5. 2026-08-09 16:33 UTCVendor advisory
  6. 2026-08-09 13:46 UTCEPSS rescore
  7. 2026-08-09 03:41 UTCEG score recompute
  8. 2026-08-09 03:41 UTCVendor advisory
  9. 2026-08-08 16:37 UTCEPSS rescore
  10. 2026-08-08 01:49 UTCEG score recompute
  11. 2026-08-08 01:49 UTCVendor advisory
  12. 2026-08-07 12:56 UTCEG score recompute
  13. 2026-08-07 12:56 UTCVendor advisory
  14. 2026-08-06 13:46 UTCEPSS rescore
  15. 2026-08-06 12:05 UTCVendor advisory
  16. 2026-08-05 23:10 UTCEG score recompute
  17. 2026-08-05 23:10 UTCVendor advisory
  18. 2026-08-05 19:17 UTCEPSS rescore
  19. 2026-08-04 15:10 UTCEPSS rescore
  20. 2026-08-04 10:38 UTCEPSS rescore
  21. 2026-08-03 21:23 UTCEG score recompute
  22. 2026-08-03 21:23 UTCVendor advisory
  23. 2026-08-03 10:36 UTCEPSS rescore
  24. 2026-08-03 01:37 UTCVendor advisory
  25. 2026-08-02 12:45 UTCEG score recompute
  26. 2026-08-02 12:45 UTCVendor advisory
  27. 2026-08-02 02:27 UTCEPSS rescore
  28. 2026-08-01 04:16 UTCEPSS rescore
  29. 2026-07-30 16:28 UTCEPSS rescore
  30. 2026-07-30 01:30 UTCEPSS rescore
  31. 2026-07-28 15:36 UTCEPSS rescore
  32. 2026-07-27 14:13 UTCEPSS rescore
  33. 2026-07-26 14:54 UTCEPSS rescore
  34. 2026-07-26 14:54 UTCEPSS rescore
  35. 2026-07-25 14:18 UTCEPSS rescore
  36. 2026-07-24 14:17 UTCEPSS rescore
  37. 2026-07-24 14:17 UTCEPSS rescore
  38. 2026-07-23 14:18 UTCEPSS rescore
  39. 2026-07-23 14:18 UTCEPSS rescore
  40. 2026-07-23 03:11 UTCEG score recompute
  41. 2026-07-22 14:08 UTCEPSS rescore
  42. 2026-07-20 17:08 UTCEPSS rescore
  43. 2026-07-20 05:10 UTCOSV refresh
  44. 2026-07-19 14:31 UTCEPSS rescore
  45. 2026-07-19 02:29 UTCEPSS rescore
  46. 2026-07-18 10:04 UTCEPSS rescore
  47. 2026-07-16 17:03 UTCEPSS rescore
  48. 2026-07-15 16:57 UTCEPSS rescore
  49. 2026-07-15 16:57 UTCEPSS rescore
  50. 2026-07-15 02:00 UTCEPSS rescore
  51. 2026-07-13 22:30 UTCEPSS rescore
  52. 2026-07-13 06:13 UTCEPSS rescore
  53. 2026-07-13 06:13 UTCEPSS rescore
  54. 2026-07-12 05:46 UTCEPSS rescore
  55. 2026-07-11 08:27 UTCEPSS rescore
  56. 2026-07-09 19:10 UTCEPSS rescore
  57. 2026-07-08 15:15 UTCEPSS rescore
  58. 2026-07-07 13:46 UTCEPSS rescore
  59. 2026-07-06 16:27 UTCEPSS rescore
  60. 2026-07-06 16:27 UTCEPSS rescore
  61. 2026-07-06 02:23 UTCEPSS rescore
  62. 2026-07-06 02:23 UTCEPSS rescore
  63. 2026-07-05 02:30 UTCEPSS rescore
  64. 2026-07-04 06:31 UTCEPSS rescore
  65. 2026-07-01 15:06 UTCEPSS rescore
  66. 2026-06-30 23:22 UTCEPSS rescore
  67. 2026-06-29 14:06 UTCEPSS rescore
  68. 2026-06-28 14:07 UTCEPSS rescore
  69. 2026-06-28 04:56 UTCEPSS rescore
  70. 2026-06-27 03:08 UTCEPSS rescore
  71. 2026-06-25 13:49 UTCEPSS rescore
  72. 2026-06-25 13:49 UTCEPSS rescore
  73. 2026-06-24 14:05 UTCEPSS rescore
  74. 2026-06-23 21:33 UTCEPSS rescore
  75. 2026-06-22 14:25 UTCEPSS rescore

Related CVEs(same vendor + same CWE)

Frequently asked(5)

What is CVE-2026-40611?
CVE-2026-40611 is a high vulnerability published on April 21, 2026. 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…
When was CVE-2026-40611 disclosed?
CVE-2026-40611 was first published in the National Vulnerability Database on April 21, 2026, with the most recent update on July 15, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-40611 actively exploited?
CVE-2026-40611 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0% probability of exploitation in the next 30 days, which ranks it in the top 73.4% of all scored CVEs.
What is the CVSS score of CVE-2026-40611?
CVE-2026-40611 has a CVSS v3 base score of 8.8 (NVD).
How do I remediate CVE-2026-40611?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-40611, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

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