CVE-2023-23924
Published: 01 February 2023
Summary
CVE-2023-23924 is a critical-severity Incorrect Behavior Order: Authorization Before Parsing and Canonicalization (CWE-551) vulnerability in Dompdf Project Dompdf. Its CVSS base score is 10.0 (Critical).
Operationally, ranked in the top 2.1% of CVEs by exploit likelihood; it is not currently listed in the CISA KEV catalog; a public proof-of-concept is referenced.
Deeper analysis
Dompdf 2.0.1, an HTML-to-PDF conversion library, contains a URI validation flaw that is bypassed during SVG parsing when an attacker supplies <image> tags containing uppercase letters. The bypass permits use of the phar:// wrapper and triggers arbitrary object unserialize on PHP versions prior to 8.0.0. The issue is tracked as CWE-551 and CWE-863 and carries a CVSS 3.1 score of 10.0.
An unauthenticated attacker who can supply a crafted SVG file to a Dompdf instance can invoke arbitrary URL schemes. On affected PHP releases this yields arbitrary deserialization, enabling at minimum file deletion and, depending on available classes, remote code execution.
The project’s security advisory and subsequent commits address the flaw by tightening URI validation; the fix is included in the v2.0.2 release. The associated EPSS score has remained near 0.5 with only minor fluctuation between its recorded peak and current value.
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2023-0610
Vulnerability details
Dompdf is an HTML to PDF converter. The URI validation on dompdf 2.0.1 can be bypassed on SVG parsing by passing `<image>` tags with uppercase letters. This may lead to arbitrary object unserialize on PHP < 8, through the `phar`…
more
URL wrapper. An attacker can exploit the vulnerability to call arbitrary URL with arbitrary protocols, if they can provide a SVG file to dompdf. In PHP versions before 8.0.0, it leads to arbitrary unserialize, that will lead to the very least to an arbitrary file deletion and even remote code execution, depending on classes that are available.
- CWE(s)
Related Threats
No named actor attribution yet. ATT&CK technique mapping in progress for this CVE.
Affected Assets
Mitigating Controls
Likely Mitigating Controls AI
Per-CVE control mapping for this CVE has not run yet; the list below is derived from the weakness types (CWEs) cited in the NVD entry.
Periodic review and update of procedures reduces incorrect authorization implementations over time.
Supervision identifies cases where authorization logic incorrectly permits unauthorized actions.
Defining permitted attribute values and auditing modifications reduces the chance of incorrect authorization outcomes due to tampered or missing labels.
The authorization process and usage restrictions help prevent incorrect authorization for remote access types.
Establishing configuration and connection requirements helps ensure correct rather than incorrect authorization for wireless access.
Establishing connection authorization processes for mobile devices helps ensure authorization decisions are correctly implemented rather than incorrect.
Monitoring account use, notifying on changes, and reviewing accounts for compliance corrects incorrect authorization assignments.
Ensures authorization decisions for external system use are correctly implemented and enforced.