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The vulnerability resides in OpenClaw’s handling of Synology Chat incoming webhooks. Prior to the fix, the webhook authentication endpoint did not enforce any rate limiting on repeated requests with invalid tokens. When a request presented an incorrect or malformed webhook token, the server immediately rejected it with an authentication failure response, but no throttling was applied between successive guesses. This allowed an attacker to send a high volume of requests in a short time, attempting to brute‑force weak or predictable webhook secrets. Because the endpoint was pre‑authentication, the attacker did not need any prior credentials to launch the attack. The missing delay between failures meant that thousands of guesses per second could be sent, significantly increasing the feasibility of brute‑forcing a token. The issue was identified in version v2026.3.24 and earlier, and the root cause was the absence of a repeated‑guess throttle before returning the auth failure. The fix, implemented in commit 0b4d07337467f4d40a0cc1ced83d45ceaec0863c, adds a throttling mechanism that limits the number of invalid attempts from a given source, delaying responses after repeated failures. This effectively blocks brute‑force attempts by making them time‑prohibitive without affecting legitimate authentication flows.
Platform: OpenClaw
Version: <= 2026.3.24
Vulnerability : Rate‑limit bypass
Severity: Moderate
date: Mar 26, 2026
Prediction: Mar 29, 2026
What Undercode Say:
Simulate brute‑force attempts against the vulnerable endpoint
for token in $(cat wordlist.txt); do
curl -X POST "https://target/synology/webhook" \
-H "Content-Type: application/json" \
-d "{\"token\":\"$token\"}"
done
After patching, throttling can be tested with a delay script
for token in $(cat wordlist.txt); do
curl -X POST "https://target/synology/webhook" \
-H "Content-Type: application/json" \
-d "{\"token\":\"$token\"}"
sleep 1 expected delay after repeated failures
done
how Exploit:
Send a high volume of requests with different webhook tokens to the Synology Chat webhook endpoint. Monitor responses; a successful guess yields a non‑authentication‑failure response (e.g., HTTP 200 with webhook execution). Since no throttling existed, an attacker could iterate through a dictionary of weak tokens rapidly.
Protection from this CVE
Upgrade OpenClaw to version 2026.3.25 or later, which includes the throttling fix (commit 0b4d073). If immediate upgrade is not possible, implement external rate limiting at the reverse proxy or firewall level to restrict the number of requests per IP to the webhook endpoint.
Impact:
Successful exploitation allows an attacker to brute‑force a weak Synology Chat webhook token, gaining unauthorized ability to post messages or execute actions via the webhook. This could lead to information disclosure, spam, or further internal abuse depending on the webhook’s privileges.
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Sources:
Reported By: github.com
Extra Source Hub:
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