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Vulnerability record · CVE-2026-55555 · published 28 July 2026

CVE-2026-55555: Dompdf project dompdf observable discrepancy vulnerability

Dompdf Project · Dompdf

Dompdf is an HTML to PDF converter for PHP. Versions 3.15 and prior are vulnerable to a File Existence Oracle attack through the manipulation of the CSS @font-face directive. By providing malicious HTML that references local files via the file:// protocol repeatedly, an attacker can trigger PHP memory exhaustion. Because Dompdf behaves differently depending on whether a referenced local file exists (an existing file is processed repeatedly until it triggers an "Allowed memory size exhausted" crash, whereas a missing file fails fast or is ignored and never hits the memory limit), an attacker can use this observable discrepancy as an oracle to enumerate sensitive files on the server regardless of CHROOT restrictions. Exploitation requires the attacker to supply unrestricted or unsanitized HTML in a request that permits large data, plus a configuration where Dompdf's memory limit is low enough to be exhausted (with  $_dompdf_show_warnings=true  making the overflow easier to reach). This issue has been fixed in version 3.16.

2.3 CVSS 4.0 Low EPSS 0.51% · top 59.0% CWE-203 · Observable discrepancy
2.3CVSS 4.0 base score
0.51%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
4References, 2 tagged exploit
5 Aug 2026Last modified by NVD

Description

Dompdf is an HTML to PDF converter for PHP. Versions 3.15 and prior are vulnerable to a File Existence Oracle attack through the manipulation of the CSS @font-face directive. By providing malicious HTML that references local files via the file:// protocol repeatedly, an attacker can trigger PHP memory exhaustion. Because Dompdf behaves differently depending on whether a referenced local file exists (an existing file is processed repeatedly until it triggers an "Allowed memory size exhausted" crash, whereas a missing file fails fast or is ignored and never hits the memory limit), an attacker can use this observable discrepancy as an oracle to enumerate sensitive files on the server regardless of CHROOT restrictions. Exploitation requires the attacker to supply unrestricted or unsanitized HTML in a request that permits large data, plus a configuration where Dompdf's memory limit is low enough to be exhausted (with  $_dompdf_show_warnings=true  making the overflow easier to reach). This issue has been fixed in version 3.16.

CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://github.com/dompdf/dompdf/commit/75c39a083bf7298044fb27399b4cc183054438b4 Patch
https://github.com/dompdf/dompdf/releases/tag/v3.1.6 Release Notes
https://github.com/dompdf/dompdf/security/advisories/GHSA-7x2p-4jvh-6384 ExploitVendor Advisory
https://github.com/dompdf/dompdf/security/advisories/GHSA-7x2p-4jvh-6384 ExploitVendor Advisory

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Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

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Source: NIST National Vulnerability Database (record CVE-2026-55555), CISA KEV, FIRST EPSS (scores of 2026-09-29). This page is refreshed as NVD updates the record.