Vulnerability in github.com/caddyserver/caddy/v2 (CVE-2026-45135)
Summary
Vulnerability in github.com/caddyserver/caddy/v2 (CVE-2026-45135). Successful exploitation can lead to full system takeover. Exploitable via search.IgnoreCase. Mitigation: upgrade to 2.11.3 or later.
Original description
The description as published by the source.
Summary
The FastCGI transport's splitPos() in modules/caddyhttp/reverseproxy/fastcgi/fastcgi.go misuses golang.org/x/text/search with search.IgnoreCase when the request path contains a non-ASCII byte. Two distinct flaws in that fallback let an attacker mislead Caddy's FastCGI splitting into treating a non-.php (or other configured split_path extension) file as a script. In any deployment where the attacker can place content into a file served via FastCGI (uploads, file storage, etc.), this can be escalated to remote code execution by crafting a URL whose path triggers either flaw.
This function was adapted from FrankenPHP's code (see the source comment) and inherits the same bugs. Both were originally reported against FrankenPHP by @KC1zs4 as GHSA-3g8v-8r37-cgjm (which absorbed the duplicate GHSA-v4h7-cj44-8fc8). Credit for finding the underlying flaws belongs to @KC1zs4.
Details
var splitSearchNonASCII = search.New(language.Und, search.IgnoreCase)
func (t Transport) splitPos(path string) int {
if len(t.SplitPath) == 0 {
return 0
}
pathLen := len(path)
for _, split := range t.SplitPath {
splitLen := len(split)
for i := range pathLen {
if path[i] >= utf…
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-2026-45135 has been found in github.com/caddyserver/caddy/v2.
Attackers can target a specific entry point like search.IgnoreCase over the network to misuse the product.
Successful exploitation can lead to full system takeover. CVSS score: 8.1/10.
What to do: upgrade github.com/caddyserver/caddy/v2 to 2.11.3 or later.
If unsure, ask your IT team or search "github.com/caddyserver/caddy/v2 CVE-2026-45135" on the vendor's site.
CVE-2026-45135 (github.com/caddyserver/caddy/v2) — CWE-176 / CVSS v3 8.1
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Attack surface: search.IgnoreCase / split_path / match / break
Patched: 2.11.3 — 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.
A vulnerability (CWE-176) exists in github.com/caddyserver/caddy/v2. Attackers reach the vulnerable code path via search.IgnoreCase without authentication.
Check the vendor advisory for the affected versions of github.com/caddyserver/caddy/v2. Attack surface: search.IgnoreCase / split_path / match / break.
Severity: High (CVSS 8.1/10). Successful exploitation can lead to full system takeover.
Update to 2.11.3.
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/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。 -
2Apply patch patch
Upgrade github.com/caddyserver/caddy/v2 to 2.11.3ステージング環境で 2.11.3 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
Fix status by distribution
Fixed packages published by each distribution for this CVE
- Debian DEBIAN-CVE-2026-45135 caddy Fixed in: 2.11.4-1
- Ubuntu UBUNTU-CVE-2026-45135 caddy
References
- advisory nvd.nist.gov
- package github.com
- patch github.com
- web github.com
- web github.com
- web github.com
- web github.com