Path Traversal in github.com/caddyserver/caddy/v2 (CVE-2026-52844)
Summary
Path traversal in github.com/caddyserver/caddy/v2 (CVE-2026-52844). Confidential information can be exposed externally. Exploitable via GET /private/secret.txt. Mitigation: upgrade to 2.11.4 or later.
Original description
The description as published by the source.
Summary
On Windows, Caddy path matchers treat /private\secret.txt as outside /private/*, but file_server later resolves the same request path as private\secret.txt on disk.
An unauthenticated remote client can request /private%5csecret.txt and bypass Caddy path-scoped auth/deny routes protecting /private/*.
Details
The mismatch is between two Caddy code paths:
MatchPath.MatchWithError()comparesr.URL.Pathusing URL path semantics and does not normalize\to/:modules/caddyhttp/matchers.go:429,:436,:490,:532.- If the route matcher misses, Caddy skips that route:
modules/caddyhttp/routes.go:271. file_serverthen maps the same request path to a filesystem path withSanitizedPathJoin(root, r.URL.Path):modules/caddyhttp/fileserver/staticfiles.go:294,modules/caddyhttp/caddyhttp.go:257,:263.- On Windows, Go filesystem path handling treats
\as a separator, so the default filesystem opens the file under the protected directory:internal/filesystems/os.go:18.
This is related to, but distinct from, GHSA-4xrr-hq4w-6vf4 / CVE-2026-27585. That advisory fixed backslash handling in the file matcher / try_files glob path. This report does not use try_files or the file matcher; it affects ordinary path route matchers in front of direct file_server serving and reproduces on current HEAD.
PoC
Tested on current HEAD 6c675e29f87cbe7326983ddb6d739175119d394c with a Windows caddy.exe built from this re…
Source: GitHub Security Advisories (Global) 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-2026-52844 has been found in github.com/caddyserver/caddy/v2.
Attackers can target a specific entry point like GET /private/secret.txt over the network to misuse the product.
Confidential information can be exposed externally. CVSS score: 7.5/10.
What to do: upgrade github.com/caddyserver/caddy/v2 to 2.11.4 or later.
If unsure, ask your IT team or search "github.com/caddyserver/caddy/v2 CVE-2026-52844" on the vendor's site.
CVE-2026-52844 (github.com/caddyserver/caddy/v2) — CWE-22 / CVSS v3 7.5
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Attack surface: GET /private/secret.txt / GET /private / path / file_server
Patched: 2.11.4 — 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/caddyserver/caddy/v2. Attackers reach the vulnerable code path via GET /private/secret.txt without authentication.
Check the vendor advisory for the affected versions of github.com/caddyserver/caddy/v2. Attack surface: GET /private/secret.txt / GET /private / path / file_server.
Severity: High (CVSS 7.5/10). Confidential information can be exposed externally.
Update to 2.11.4.
Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.
Search webserver/proxy logs for unusual GET /private/secret.txt requests with malformed payloads or SQL meta-characters. Run grep -r 'github.com/caddyserver/caddy/v2' . 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
-
1Identify exposure identify
grep -r 'github.com/caddyserver/caddy/v2' . | 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/caddyserver/caddy/v2を grep し、稼働しているサービス・バージョンを把握する。 -
2Hunt for indicators of compromise detect
grep 'GET /private/secret.txt' /var/log/nginx/access.log | grep -E '(unusual_payload|sqli_pattern)'アクセスログで
GET /private/secret.txtへの異常なリクエスト (不正な認証ヘッダ・SQLメタ文字)を過去 30〜90日分捜索。WAF/SIEM があれば該当パスのアラート発火履歴を確認。 -
3Apply patch patch
Upgrade github.com/caddyserver/caddy/v2 to 2.11.4ステージング環境で 2.11.4 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と、Step 2 で見つけた異常検知の続報チェックを含めること。
-
4Post-deployment verification verify
Replay attack against GET /private/secret.txt on staging to confirm patch closes the vector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 Step 2 と同じログクエリでアラート再発が無いか継続監視。
Affected packages
Fix status by distribution
Fixed packages published by each distribution for this CVE
- Ubuntu UBUNTU-CVE-2026-52844 caddy
References
- advisory nvd.nist.gov
- package github.com
- web github.com
- web github.com