CVE-2026-59942 Dompdf: Denial of Service (DoS) via Resource Exhaustion using Oversized Image Bitmaps

What is CVE-2026-59942?

CVE-2026-59942 is a medium-severity denial of service vulnerability in dompdf, published on 28 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

Official description

Dompdf is an HTML to PDF converter for PHP. Versions 3.15 and prior are vulnerable to a Denial of Service (DoS) attack via resource exhaustion. An attacker can crash the PHP process by providing a specially crafted HTML document containing a single image with massive dimensions (e.g., 30,000x30,000 pixels). While Dompdf implements internal checks to validate image dimensions, these can be bypassed by using a high-entropy image (such as random noise) encoded in Base64 and wrapped in specific CSS containers. The vulnerability exists because the dimension validation happens early, but the resource allocation for calculating the object's bounding box and internal buffers during the rendering phase does not strictly limit the cumulative CPU time or memory usage for a single object that has passed the initial check. An unauthenticated remote attacker can cause a complete Denial of Service on the web server by submitting a crafted HTML string. This affects any application that allows users to provide HTML content or URLs that are subsequently converted to PDF using Dompdf. This issue has been fixed in version 3.16.

Weakness: CWE-400

Which versions are affected by CVE-2026-59942?

2 open source packages ship an affected version, including dompdf/dompdf. It affects 1 product.

Products include Dompdf Project Dompdf.

How do I fix CVE-2026-59942?

Upgrade dompdf/dompdf to 3.1.6 or later.

Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.

Is CVE-2026-59942 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-59942 exists.

Other vulnerabilities in dompdf

• CVE-2023-24813 URI validation failure on SVG parsing. Bypass of CVE-2023-23924 Critical 10.0
• CVE-2023-23924 URI validation failure on SVG parsing in Dompdf Critical 10.0
• CVE-2021-3838 PHAR Deserialization in dompdf/dompdf Critical 9.8
• CVE-2021-3902 Improper Restriction of XML External Entity Reference in dompdf/dompdf Critical 9.8
• CVE-2022-28368 Remote code injection in dompdf/dompdf Critical 9.8

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as DEBIAN-CVE-2026-59942, GHSA-f5gf-2cj8-52g2, UBUNTU-CVE-2026-59942.