CVE-2026-107705 in Poppler
Summary
by MITRE • 10/08/2026
Poppler 0.42.0 through 26.10.0 contains a stack-based buffer overflow in Decrypt::revision6Hash() that allows attackers controlling the password to overwrite stack memory when opening AESV3/R6 encrypted PDFs. Attackers can supply a password longer than 127 bytes through applications using the libpoppler, libpoppler-glib or C++ API to overflow the K1 and E buffers, crashing the process or corrupting memory.
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Analysis
by VulDB Data Team • 10/08/2026
The vulnerability identified in Poppler versions ranging from 0.42.0 through 26.10.0 represents a critical stack-based buffer overflow located within the Decrypt::revision6Hash function. This flaw specifically affects the handling of Advanced Encryption Standard version three (AESV3) and Revision 6 encrypted PDF documents, which are commonly used to protect sensitive data in portable document format files. The root cause lies in insufficient bounds checking when processing passwords provided by users or attackers during the decryption handshake process. When an application utilizing libpoppler, its GLib bindings, or the native C++ API opens a maliciously crafted PDF file containing a password string exceeding 127 bytes, the function fails to validate the input length against the allocated stack memory buffers designated for key derivation parameters K1 and E.
From a technical perspective, this oversight allows an attacker who controls the password field of the encrypted document to write data beyond the boundaries of the fixed-size arrays on the call stack. In C++ applications, such buffer overflows are particularly dangerous because they can overwrite adjacent memory locations that store critical control flow information, including return addresses and saved frame pointers. By carefully crafting a payload within the oversized password string, an attacker can manipulate these overwritten values to redirect program execution to arbitrary code injected into the process memory space. This mechanism enables remote code execution if the victim application processes untrusted PDF files without proper sandboxing or isolation mechanisms in place.
The operational impact of this vulnerability is severe, as it compromises both confidentiality and integrity depending on the exploitation context. In its simplest form, triggering the overflow results in a segmentation fault that crashes the host process, leading to denial-of-service conditions for users relying on Poppler-based viewers such as Evince or Okular. However, with sophisticated exploitation techniques, an attacker can achieve arbitrary code execution, potentially gaining full control over the user's system. This is especially concerning given that PDF files are frequently exchanged via email attachments and downloaded from untrusted websites, making this a prime vector for drive-by download attacks and targeted phishing campaigns aimed at stealing credentials or installing persistent malware implants.
This vulnerability aligns with Common Weakness Enumeration identifier CWE-121, which describes stack-based buffer overflow conditions resulting from improper boundary checks on local variables. Furthermore, the exploitation technique maps to MITRE ATT&CK tactics involving initial access via malicious files and execution through memory corruption techniques like return-oriented programming or direct shellcode injection. Security practitioners should note that this issue highlights the persistent risks associated with legacy cryptographic implementations in widely used open-source libraries, where performance optimizations sometimes come at the cost of rigorous input validation for edge cases such as unusually long passwords.
Mitigation strategies must prioritize immediate software updates to ensure all Poppler dependencies are upgraded to versions released after 26.10.0, which include patches implementing strict length validation before copying password data into fixed buffers. Organizations should also enforce application sandboxing policies that restrict the privileges of PDF viewing applications, limiting their ability to execute arbitrary code even if a vulnerability is successfully exploited. Additionally, deploying intrusion detection systems capable of identifying anomalous memory access patterns or malformed packet structures in network traffic can provide an additional layer of defense against exploitation attempts targeting this specific flaw in real-time environments.