GHSA-fj2m-qvh9-jq4q local-deep-research is Vulnerable to HTML Injection via Unescaped User Input in PDF Export (`pdf_service.py:_markdown_to_html`)
Summary`PDFService._markdown_to_html()` constructs an HTML document by interpolating user-controlled values — specifically `title` (sourced from `research.title` or `research.query`) and `metadata` key-value pairs — directly into an f-string without any HTML escaping. An authenticated attacker can craft a research query containing HTML special characters to inject arbitrary HTML tags into the document processed by WeasyPrint during PDF export. This injection can be chained to trigger a Server-Side Request Forgery (SSRF), bypassing the application's existing SSRF defenses in `ssrf_validator.py`.Details**Vulnerable code:** `src/local_deep_research/web/services/pdf_service.py`, lines 171–176**Data flow trace:**`research.query` is a string submitted by the user via `POST /api/start_research`, stored as-is in the database, and retrieved without any sanitization. When the user triggers `POST /api/v1/research/<research_id>/export/pdf`, this value is embedded unescaped into the HTML document processed by WeasyPrint.**Injection point 1: `<title>` tag breakout**When WeasyPrint encounters the injected `<img>` tag, it issues an HTTP GET request to the value of `src` by default.**Injection point 2: `<meta>` attribute breakout**WeasyPrint will fetch and apply the external stylesheet, which also constitutes SSRF.Proof of Concept**Step 1: Log in and submit a research query containing the injection payload**The response returns a `research_id`, e.g. `"aaaa-bbbb-cccc-dddd"`.**Step 2: After the research completes, trigger PDF export****Step 3: Intermediate HTML constructed server-side****Step 4: WeasyPrint issues an outbound HTTP request to the injected URL**Observed in network monitoring (e.g. `tcpdump`) or the target internal service logs:**Lightweight verification (no SSRF environment required):**Set the query to:The resulting HTML will contain two `<title>` tags and the PDF document metadata title will read `INJECTED`, confirming successful injection.Impact1. Chained SSRF (High Severity)By injecting `<img src>`, `<link href>`, or `<style>@import url()` tags pointing to internal addresses, WeasyPrint will issue HTTP requests on behalf of the server during PDF generation. This allows access to:**Cloud metadata services** (`169.254.169.254`) on AWS, GCP, or Azure — enabling theft of IAM credentials and instance identity documents.**Internal network services** (`192.168.x.x`, `10.x.x.x`) — enabling reconnaissance and interaction with internal APIs not exposed to the internet.**Localhost administrative interfaces** — if SSRF protections are only applied at the user-input validation layer.This is an effective bypass of the application's existing SSRF defenses in `ssrf_validator.py`, because WeasyPrint's outbound resource requests are never routed through that validator.2. HTML Document Structure CorruptionInjected tags can prematurely close `<head>` and insert arbitrary content into `<body>`, causing WeasyPrint to render incorrectly or crash, resulting in a Denial of Service (DoS) condition for the export functionality.3. CSS Injection (Medium Severity)By injecting `<link>` or `<style>` tags that load external stylesheets, an attacker can fully control the visual content of the generated PDF, enabling report content forgery or spoofing.4. Affected ScopeAll PDF export operations are affected.The vulnerability is reachable by any authenticated user — no elevated privileges required.Because each user operates against their own encrypted database, cross-user exploitation is not possible. However, on any shared or multi-tenant deployment, every authenticated user can independently trigger this vulnerability.RemediationApply `html.escape()` to all user-controlled values before embedding them in the HTML template inside `_markdown_to_html`:Additionally, consider configuring WeasyPrint with a custom `url_fetcher` that blocks or restricts outbound HTTP requests to prevent SSRF via injected or legitimately-embedded external resources:*Report generated against commit `f3540fb3` — local-deep-research, branch `main`.*Maintainer note (2026-04-24)Thanks @Firebasky for the detailed report. The complete remediation spans two PRs, both merged to `main`:**#3082** (merged 2026-03-29, shipped in **v1.5.0+**) — closes the HTML-injection sinks:`html.escape()` now wraps the `title` value in `<title>…</title>`Same for metadata keys/values in `<meta name="…" content="…">`Regression tests added in `tests/web/services/test_pdf_service.py`**#3613** (merged 2026-04-24, shipped in **v1.6.0**) — implements the `url_fetcher` recommendation from the Remediation section:New `_safe_url_fetcher` in `pdf_service.py` delegates to `weasyprint.default_url_fetcher` only after `security.ssrf_validator.validate_url` accepts the URLBlocks AWS metadata (169.254.169.254), RFC1918, loopback, and non-http(s) schemesCovers the chained SSRF path through any URL reaching the rendered HTML — markdown body, citations, raw-HTML passthrough via Python-MarkdownBlocked URLs raise `UnsafePDFResourceURLError` (a `ValueError` subclass) so WeasyPrint skips the resource and the render continues8 regression tests, including an end-to-end render with `<img src="http://169.254.169.254/…">` embedded in the body**Advisory metadata:** CVSS `CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:N/A:N` (5.0 Moderate), CWEs **CWE-79** + **CWE-918**. **Patched in v1.6.0** — upgrade to v1.6.0 or later to receive both fixes.
CVSS v3.1 score: 5