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UK Cyber Defence
VulnerabilityAnalyzed

CVE-2026-55555

Versions 3.15 and prior are vulnerable to a File Existence Oracle attack through the manipulation of the CSS @font-face directive.

LOW 2.3EPSS 0.35%

Does this matter?

Lower severity and a low EPSS score (0.35%). Track it; it rarely justifies an emergency change on its own.

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
2.3 LOWCVSS: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/M
EPSS
0.35% probability · 29th percentile
CISA KEV
Not listed
Weakness
CWE-203
Affected
dompdf project/dompdf
Source
security-advisories@github.com

References

Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.