Vulnerability in dompdf/dompdf (CVE-2026-55555)
Summary
Vulnerability in dompdf/dompdf (CVE-2026-55555). Confidential information can be exposed externally. Exploitable via CHROOT. Mitigation: upgrade to 3.1.6 or later.
Original description
The description as published by the source.
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.
Source: GitHub Security Advisories (Global) 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-2026-55555 has been found in dompdf/dompdf.
Attackers can target a specific entry point like CHROOT over the network to misuse the product.
Confidential information can be exposed externally. CVSS score: 7.5/10.
What to do: upgrade dompdf/dompdf to 3.1.6 or later.
If unsure, ask your IT team or search "dompdf/dompdf CVE-2026-55555" on the vendor's site.
CVE-2026-55555 (dompdf/dompdf) — CWE-203 / CVSS v3 7.5
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Attack surface: CHROOT / index.php / response.pdf
Patched: 3.1.6 — 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.
A vulnerability (CWE-203) exists in dompdf/dompdf. Attackers reach the vulnerable code path via CHROOT without authentication.
Check the vendor advisory for the affected versions of dompdf/dompdf. Attack surface: CHROOT / index.php / response.pdf.
Severity: High (CVSS 7.5/10). Confidential information can be exposed externally.
Update to 3.1.6.
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 'dompdf/dompdf' . 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
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1Identify exposure identify
grep -r 'dompdf/dompdf' . | 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
dompdf/dompdf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 dompdf/dompdf to 3.1.6ステージング環境で 3.1.6 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。
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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
Fix status by distribution
Fixed packages published by each distribution for this CVE
- Debian DEBIAN-CVE-2026-55555 php-dompdf
- Ubuntu UBUNTU-CVE-2026-55555 php-dompdf
References
- advisory github.com
- advisory github.com
- advisory nvd.nist.gov
- package github.com
- patch github.com
- web github.com
- web github.com