CVSS 3.1
8.2 highCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:NCVE-2026-48126
High (8.2). EPSS 0.3% chance of exploitation in the next 30 days. Fixed in github.com/xyproto/algernon 1.17.8.
Algernon is a small self-contained pure-Go web server. Prior to 1.17.8, when algernon is started with --domain (or --letsencrypt, which silently turns on --domain at engine/flags.go:372), the request handler resolves the served directory by joining the configured --dir with the value of the client-supplied Host header. The join is performed by filepath.Join with no validation, so a Host: .. header walks one level above the document root. Subsequent file resolution then exposes everything in that parent directory — arbitrary file read, full directory listing, and, if any .lua file is present, server-side Lua execution. This vulnerability is fixed in 1.17.8.
Severity
- EPSS
- 0.3% chance of exploitation in the next 30 days; higher than 26% of CVEs (scores of 2026-10-31)
- CWEs
- CWE-22, CWE-23, CWE-644
- Published
- Modified
- Record from
- the NVD, synced
Packages (OSV)
| Advisory | Ecosystem | Package | Affected | Fixed in |
|---|---|---|---|---|
| GHSA-jc3j-x6pg-4hmv | Go | github.com/xyproto/algernon | <1.17.8 | 1.17.8 |
| GO-2026-5460 | Go | github.com/xyproto/algernon | <1.17.8 | 1.17.8 |