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GHSA-36mm-w85j-3q2j
No affected components available
Summary
Description An XML External Entity Injection (CWE-611) vulnerability in veraPDF allows a remote attacker to read arbitrary files on the server file system and perform Server-Side Request Forgery by submitting a crafted PDF containing a malicious XFA stream. This affects all current versions of veraPDF-validation.
Details
The vulnerability resides in veraPDF-validation validation-model/src/main/java/org/verapdf/gf/model/impl/pd/GFPDAcroForm.java within the getdynamicRender() method. This method retrieves the /XFA entry from the PDF's /AcroForm dictionary, decodes the embedded XML stream, and parses it to extract the <dynamicRender> element value.
The vulnerability stems from the use of a default-configured DocumentBuilderFactory to parse fully attacker-controlled XML:
- The factory is created via
DocumentBuilderFactory.newInstance()with no security features enabled. disallow-doctype-decl, external-general-entities, external-parameter-entities, and FEATURE_SECURE_PROCESSING are all left at their insecure defaults. - The input passed to
builder.parse()is the decoded /XFA stream taken directly from the untrusted PDF. - The text content of the
<dynamicRender>node is returned to the validation model. Note that the shipped PDF/UA-1 rule (dynamicRender != 'required') consumes this value but does not echo it into the report output, so reliable exfiltration requires the out-of-band parameter-entity technique described under Impact rather than in-band reflection.
Impact
This impacts all current releases of the veraPDF validation-model module.
Successful exploitation requires only that the target validate an attacker-supplied PDF against the PDF/UA-1 profile (or via flavour auto-detection on a PDF that declares PDF/UA-1 conformance), since getdynamicRender() is invoked by the dynamicRender != 'required' rule in the bundled PDF/UA-1 profile. No additional configuration or operator action is required.
Proposed Patch
Harden the DocumentBuilderFactory in validation-model/src/main/java/org/verapdf/gf/model/impl/pd/GFPDAcroForm.java per the OWASP XXE Prevention Cheat Sheet to disallow DOCTYPE outright.
The vulnerability can be exploited over the network without needing physical access. It is easy for an attacker to exploit this vulnerability. An attacker does not need any special privileges or access rights. No user interaction is needed for the attacker to exploit this vulnerability.
Exploitation attempts have been detected. Elevated vigilance and prompt remediation are advised.
The exploit probability is very low. The vulnerability is unlikely to be exploited in the next 30 days.
We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.
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