CVE-2026-55537: PraisonAI: Webhook SSRF via DNS fail-open in `JobSubmitRequest.validate_webhook_url()` — bypass of CVE-2026-40114

praisonai/jobs/models.py::JobSubmitRequest.validate_webhook_url() validates webhook URLs by resolving the hostname and checking whether the IP is private. When DNS resolution fails (socket.gaierror), the validator silently passes the URL via except socket.gaierror: pass. Additionally, even when DNS succeeds at validation time, the webhook is fired much later by JobExecutor._send_webhook(), which calls httpx.AsyncClient().post(job.webhook_url) — performing a fresh, independent DNS lookup at execution time. Together, these flaws create a TOCTOU SSRF window.

An attacker can:

1. Submit a job with webhook_url pointing to a hostname that currently does not resolve (NXDOMAIN) → validation passes (gaierror → pass)
2. Update DNS to point that hostname to 127.0.0.1 or another private IP
3. When the job completes, _send_webhook() resolves the hostname fresh → POST sent to the internal IP