CVE-2026-59943
Fix: dompdf/dompdf@6a58996CVE-2026-59943 is a CWE-209 vulnerability in dompdf/dompdf. O3 Security confirms whether CVE-2026-59943 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
Dompdf: Embedded SVG images can leak existence of files and directories within the filesystem
Exploitation Status
Proof-of-concept exploit code exists
- CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-59943.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
Real-World Exposure
dompdf/dompdfReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Packagist packages — download data is not available via public APIs for these ecosystems.
Description
Dompdf is an HTML to PDF converter for PHP. In versions 3.15 and prior, if a malicious actor can supply unrestricted content for rendering by Dompdf they can utilize the SVG rendering functionality to leak filesystem information when rendering PDF files using image references within a data-URI encoded SVG document. Using an <image> element inside a data-URI embedded SVG, an attacker can attempt to embed other files via the href or xlink:href attributes. When processing a file that does not exist (e.g. file:///DOESNOTEXIST), dompdf behaves differently than it does when accessing a file or directory that actually exists on the filesystem. This issue has been fixed in version 3.16.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐘Packagist | dompdf/dompdf | all versions | 3.1.6 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for dompdf/dompdf. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update dompdf/dompdf to 3.1.6 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-59943 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether CVE-2026-59943 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to CVE-2026-59943. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2026-59943 in your dependencies?
O3 detects CVE-2026-59943 across Packagist dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.