Path Traversal in github.com/xyproto/algernon (CVE-2026-48126)
Summary
Path traversal in github.com/xyproto/algernon (CVE-2026-48126). Confidential information can be exposed externally. Exploitable via Host header. Mitigation: upgrade to 1.17.8 or later.
Original description
The description as published by the source.
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.
Source: NIST National Vulnerability Database NVD GitHub Advisory
Auto-generated summary
Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.
A vulnerability tracked as CVE-2026-48126 has been found in github.com/xyproto/algernon.
Attackers can target a specific entry point like Host header over the network to misuse the product.
Confidential information can be exposed externally. CVSS score: 8.2/10.
What to do: upgrade github.com/xyproto/algernon to 1.17.8 or later.
If unsure, ask your IT team or search "github.com/xyproto/algernon CVE-2026-48126" on the vendor's site.
CVE-2026-48126 (github.com/xyproto/algernon) — CWE-22 / CVSS v3 8.2
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Attack surface: Host header / Host / filepath.Join / RegisterHandlers
Patched: 1.17.8 — apply immediately
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.
Path traversal (CWE-22) exists in github.com/xyproto/algernon. Attackers reach the vulnerable code path via Host header without authentication.
Check the vendor advisory for the affected versions of github.com/xyproto/algernon. Attack surface: Host header / Host / filepath.Join / RegisterHandlers.
Severity: High (CVSS 8.2/10). Confidential information can be exposed externally.
Update to 1.17.8.
Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.
Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Run grep -r 'github.com/xyproto/algernon' . against your dependency files (package-lock.json, requirements.txt, go.sum) to find affected services.
Response actions
Concrete steps and command examples for SOC/SRE teams to execute in order
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1Identify exposure identify
grep -r 'github.com/xyproto/algernon' . | grep -v node_modulesリポジトリと本番環境の依存ファイル (package-lock.json / requirements.txt / go.sum / Gemfile.lock 等) で
github.com/xyproto/algernonを grep し、稼働しているサービス・バージョンを把握する。 -
2Apply patch patch
Upgrade github.com/xyproto/algernon to 1.17.8ステージング環境で 1.17.8 に上げて回帰テスト → 本番反映。回帰テストはアプリの主要ハッピーパスを含めること。
-
3Post-deployment verification verify
Confirm patched version is live in productionパッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。
Affected packages
References
- advisory github.com
- advisory nvd.nist.gov
- advisory github.com
- package github.com
- web github.com