CVE-2017-11627 in QPDF
Summary
by MITRE
A stack-consumption vulnerability was found in libqpdf in QPDF 6.0.0, which allows attackers to cause a denial of service via a crafted file, related to the PointerHolder function in PointerHolder.hh, aka an "infinite loop."
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Analysis
by VulDB Data Team • 12/14/2022
The vulnerability CVE-2017-11627 represents a critical stack-consumption issue within the QPDF library version 6.0.0 that manifests as an infinite loop condition. This flaw specifically affects the PointerHolder function located in the PointerHolder.hh header file, creating a scenario where maliciously crafted PDF files can trigger excessive stack memory consumption. The vulnerability operates by exploiting the way the library handles object references and memory management during PDF parsing operations, leading to a situation where the stack grows uncontrollably until system resources are exhausted.
From a technical perspective, this vulnerability aligns with CWE-772, which describes insufficient resource management, and more specifically with CWE-835, which addresses infinite loops or iterations that do not terminate properly. The flaw occurs when the PointerHolder class fails to properly validate or limit the depth of recursive operations or object references during PDF file processing. Attackers can construct malicious PDF files that contain circular references or deeply nested structures that cause the PointerHolder function to repeatedly call itself or consume stack space without proper termination conditions, ultimately leading to stack overflow and system instability.
The operational impact of this vulnerability extends beyond simple denial of service, as it can be exploited to disrupt services that rely on QPDF for PDF processing and manipulation. Systems that process untrusted PDF files, such as email servers, document management platforms, and web applications that accept PDF uploads, become vulnerable to this attack vector. The infinite loop condition can cause applications to become unresponsive or crash entirely, potentially allowing attackers to perform persistent denial of service attacks against critical infrastructure. This vulnerability is particularly concerning in environments where automated PDF processing occurs, as it can be exploited through automated means to overwhelm system resources continuously.
Mitigation strategies for CVE-2017-11627 should focus on immediate patching of affected QPDF library versions, with the release of QPDF 7.0.0 addressing this specific stack consumption issue. Organizations should implement proper input validation and sanitization measures when processing PDF files, including setting resource limits and timeout mechanisms for PDF parsing operations. The ATT&CK framework categorizes this vulnerability under T1499.004, which covers network denial of service, and T1566.001, which addresses spearphishing attachments, as attackers may use malicious PDF files to exploit this vulnerability. Additionally, implementing sandboxing mechanisms for PDF processing and monitoring stack usage patterns can provide additional defense layers against exploitation attempts. System administrators should also consider implementing automated monitoring solutions that can detect unusual resource consumption patterns that may indicate exploitation attempts.