SSRF (Server-Side Request Forgery) in weasyprint (CVE-2026-55073)
Summary
SSRF in weasyprint (CVE-2026-55073). Confidential information can be exposed externally. Exploitable via url_fetcher. Mitigation: upgrade to 70.0 or later.
Original description
The description as published by the source.
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-lo…
Source: NIST National Vulnerability Database NVD GitHub Advisory
Auto-generated summary
Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.
A vulnerability tracked as CVE-2026-55073 has been found in weasyprint.
Attackers can target a specific entry point like url_fetcher over the network to misuse the product.
Confidential information can be exposed externally. CVSS score: 6.2/10.
What to do: upgrade weasyprint to 70.0 or later.
If unsure, ask your IT team or search "weasyprint CVE-2026-55073" on the vendor's site.
CVE-2026-55073 (weasyprint) — CWE-918 / CVSS v3 6.2
Attack vector: local / unauthenticated / no user interaction
Attack surface: url_fetcher / main / xmp_metadata / stylesheets
Patched: 70.0 — apply immediately
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.
SSRF (CWE-918) exists in weasyprint. Attackers reach the vulnerable code path via url_fetcher without authentication.
Check the vendor advisory for the affected versions of weasyprint. Attack surface: url_fetcher / main / xmp_metadata / stylesheets.
Severity: Medium (CVSS 6.2/10). Confidential information can be exposed externally.
Update to 70.0.
Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.
Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Run grep -r 'weasyprint' . against your dependency files (package-lock.json, requirements.txt, go.sum) to find affected services.
Response actions
Concrete steps and command examples for SOC/SRE teams to execute in order
-
1Identify exposure identify
grep -r 'weasyprint' . | grep -v node_modulesリポジトリと本番環境の依存ファイル (package-lock.json / requirements.txt / go.sum / Gemfile.lock 等) で
weasyprintを grep し、稼働しているサービス・バージョンを把握する。 -
2Apply patch patch
Upgrade weasyprint to 70.0ステージング環境で 70.0 に上げて回帰テスト → 本番反映。回帰テストはアプリの主要ハッピーパスを含めること。
-
3Post-deployment verification verify
Confirm patched version is live in productionパッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。
Affected packages
References
- web security-advisories@github.com
- web github.com
- web github.com
- web github.com