CVE-2019-20834 in PhantomPDF
Summary
by MITRE
An issue was discovered in Foxit PhantomPDF before 8.3.10. It allows signature validation bypass via a modified file or a file with non-standard signatures.
Once again VulDB remains the best source for vulnerability data.
Analysis
by VulDB Data Team • 10/22/2020
The vulnerability identified as CVE-2019-20834 represents a critical security flaw in Foxit PhantomPDF software versions prior to 8.3.10, specifically targeting the document signature validation mechanism. This issue stems from insufficient validation procedures that fail to properly verify the integrity and authenticity of digital signatures within PDF documents. The flaw allows malicious actors to bypass signature verification processes through two primary methods: modifying existing signed files or creating new documents with non-standard signature formats that the software accepts without proper scrutiny.
This vulnerability operates at the core of PDF security protocols and falls under the category of signature validation bypass as classified by CWE-347, which deals with improper verification of cryptographic signatures. The technical implementation flaw lies in the software's failure to maintain strict adherence to PDF signature standards during the validation process, allowing attackers to exploit weaknesses in the signature parsing and verification algorithms. The software's signature validation system appears to accept malformed or altered signature structures that should have been rejected during the integrity check phase, creating a pathway for unauthorized document modifications to go undetected.
The operational impact of this vulnerability extends beyond simple document integrity concerns, as it undermines the fundamental trust model that digital signatures are designed to provide. Attackers can manipulate signed PDF documents without detection, potentially compromising legal documents, contracts, or sensitive business communications that rely on signature authenticity. This vulnerability particularly affects organizations that depend on PDF signatures for compliance purposes, as it allows for the creation of fraudulent documents that appear legitimate to systems using affected Foxit PhantomPDF versions. The security implications include potential financial fraud, legal disputes, and regulatory compliance violations when signed documents are manipulated without proper detection mechanisms.
Organizations utilizing Foxit PhantomPDF software before version 8.3.10 should immediately implement mitigations including mandatory software updates to the patched version, enhanced document review procedures, and implementation of additional verification layers beyond the software's built-in signature validation. The ATT&CK framework categorizes this vulnerability under T1553.004 - Credentials from Password Stores, as it represents an indirect method of credential compromise through document integrity manipulation. Additionally, organizations should consider implementing automated document integrity checking tools and establishing clear protocols for handling sensitive signed documents. The vulnerability demonstrates the critical importance of maintaining up-to-date security patches and highlights the necessity of robust signature validation mechanisms in enterprise document management systems.