Skip to content

🛡️ Sentinel: Fix SSRF bypass and add DoS protection to URL capture #40

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Draft
Sumit-5002 wants to merge 1 commit into
base: main
Choose a base branch
from
Draft

🛡️ Sentinel: Fix SSRF bypass and add DoS protection to URL capture #40

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
5 changes: 5 additions & 0 deletions .jules/sentinel.md
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -27,3 +27,8 @@
**Vulnerability:** The `/api/image/html-to-image` endpoint was vulnerable to Server-Side Request Forgery (SSRF). Initial mitigation was bypassable via DNS rebinding and non-standard loopback addresses (e.g., 127.0.0.2).
**Learning:** Checking a resolved IP before fetching is insufficient due to TOCTOU (Time-of-Check Time-of-Use) vulnerabilities where the DNS record changes between check and fetch.
**Prevention:** Use the resolved and validated IP directly in the `fetch` call and provide the original hostname in the `Host` header. Ensure IP validation covers the entire `127.0.0.0/8` range and IPv4-mapped IPv6 addresses.

## 2026-03-27 - [Multi-layered SSRF and DoS Hardening in URL Capture]
**Vulnerability:** The `/api/image/html-to-image` endpoint was vulnerable to SSRF bypasses via redirects (`redirect: 'follow'`) and lacked resource limits (timeouts/size limits), leading to potential DoS. Additionally, the internal IP blacklist was incomplete, missing ranges like CGNAT (100.64.0.0/10).
**Learning:** Security controls for fetch-based utilities must be multi-layered: validating the initial IP is insufficient if redirects are followed or if the response size/time is unbounded.
**Prevention:** Always use `redirect: 'manual'` for SSRF-sensitive fetches. Enforce strict `AbortSignal` timeouts and content size limits (e.g., 512KB). Expand internal IP checks to include all restricted ranges (RFC 1918, RFC 6598, RFC 3927, RFC 2544).
Loading
Loading