CVE-2026-34367

HighPublic PoC

Published: 31 March 2026

Published

31 March 2026

Modified

09 April 2026

KEV Added

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Patch

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CVSS Score 7.6 CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:L/A:N

EPSS Score 0.0004 11.1th percentile

Risk Priority 15 60% EPSS · 20% KEV · 20% CVSS

Summary

CVE-2026-34367 is a high-severity SSRF (CWE-918) vulnerability in Invoiceshelf Invoiceshelf. Its CVSS base score is 7.6 (High).

Operationally, exploitation aligns with the MITRE ATT&CK technique Exploit Public-Facing Application (T1190); ranked at the 11.1th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog; a public proof-of-concept is referenced.

The strongest mitigations our analysis identified are NIST 800-53 SC-7 (Boundary Protection) and SI-10 (Information Input Validation).

Threat & Defense at a Glance

What attackers do: exploitation maps to Exploit Public-Facing Application (T1190) and 1 other technique. What defenders deploy: see the NIST 800-53 controls recommended below.

Threat & Defense Details

Mitigating Controls (NIST 800-53 r5)AI

SI-10 Information Input Validation good match

prevent

Validates and sanitizes user-supplied HTML in the invoice Notes field to prevent malicious markup from causing the Dompdf library to fetch arbitrary remote resources.

SI-2 Flaw Remediation good match

prevent

Remediates the SSRF flaw by applying patches like version 2.2.0, which sanitizes input before passing to Dompdf.

SC-7 Boundary Protection good match

preventdetect

Monitors and controls outbound communications at the system boundary to block unauthorized server-initiated requests to remote or internal resources triggered by SSRF.

MITRE ATT&CK Enterprise TechniquesAI

T1190 Exploit Public-Facing Application Initial Access

Adversaries may attempt to exploit a weakness in an Internet-facing host or system to initially access a network.

attack.mitre.org →

T1522 Cloud Instance Metadata API Credential Access

Adversaries may attempt to access the Cloud Instance Metadata API to collect credentials and other sensitive data.

attack.mitre.org →

Why these techniques?

SSRF vulnerability in public-facing web app directly enables exploitation of the application for initial access (T1190) and access to internal/cloud metadata services (T1522).

Confidence: HIGH · MITRE ATT&CK Enterprise v18.1

NVD Description

InvoiceShelf is an open-source web & mobile app that helps track expenses, payments and create professional invoices and estimates. Prior to version 2.2.0, a Server-Side Request Forgery (SSRF) vulnerability exists in the Invoice PDF generation module. User-supplied HTML in the…

invoice Notes field is passed unsanitised to the Dompdf rendering library, which will fetch any remote resources referenced in the markup. This can be triggered via the PDF preview and email delivery endpoints. This issue has been patched in version 2.2.0.

Deeper analysisAI

CVE-2026-34367 is a Server-Side Request Forgery (SSRF) vulnerability, classified under CWE-918, affecting InvoiceShelf, an open-source web and mobile application for tracking expenses, payments, and generating professional invoices and estimates. The issue resides in the Invoice PDF generation module prior to version 2.2.0, where user-supplied HTML entered in the invoice Notes field is passed unsanitized to the Dompdf rendering library. This allows the library to fetch arbitrary remote resources referenced in the markup during PDF processing.

The vulnerability can be exploited by authenticated users with high privileges (PR:H) over the network (AV:N) with low complexity (AC:L) and no user interaction required (UI:N). Attackers can trigger it via the PDF preview or email delivery endpoints, causing the server to make unintended requests to remote resources. Successful exploitation leads to high confidentiality impact (C:H) with a changed scope (S:C), potentially allowing access to internal services or metadata, alongside low integrity impact (I:L) and no availability impact (A:N), as reflected in the CVSS v3.1 base score of 7.6.

The GitHub security advisory (GHSA-q9wx-ggwq-mcgh) and release notes for version 2.2.0 confirm that the issue has been patched by sanitizing the user-supplied HTML in the Notes field before passing it to Dompdf, preventing unauthorized remote resource fetches. Security practitioners should upgrade to InvoiceShelf 2.2.0 or later and review access controls for invoice editing features.