CVE-2015-8659 in iOS
Summary
by MITRE
The idle stream handling in nghttp2 before 1.6.0 allows attackers to have unspecified impact via unknown vectors, aka a heap-use-after-free bug.
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Analysis
by VulDB Data Team • 07/11/2022
The vulnerability identified as CVE-2015-8659 represents a critical heap-use-after-free issue within the nghttp2 library version 1.6.0 and earlier. This flaw resides in the idle stream handling mechanism of the HTTP/2 protocol implementation, which is a core component of modern web infrastructure. The nghttp2 library serves as a fundamental building block for HTTP/2 communication, widely adopted by servers, clients, and applications requiring high-performance HTTP/2 capabilities. The vulnerability manifests when the library processes idle streams, creating conditions where memory allocated to stream structures can be freed while still being referenced, leading to unpredictable behavior that attackers can potentially exploit for malicious purposes.
The technical nature of this heap-use-after-free vulnerability stems from improper memory management within the stream lifecycle handling code. When streams transition to idle states and subsequently get removed from active processing, the memory management logic fails to properly account for all references to the freed memory regions. This condition creates a scenario where subsequent operations might access memory that has already been deallocated, potentially leading to memory corruption, application crashes, or in more sophisticated attack scenarios, arbitrary code execution. The unspecified impact mentioned in the CVE description indicates that the exact consequences depend on the specific memory layout and access patterns during exploitation, making the vulnerability particularly dangerous as it can be leveraged in various attack vectors.
The operational impact of this vulnerability extends significantly across the HTTP/2 ecosystem, as nghttp2 is integrated into numerous web servers, proxy implementations, and client applications. Systems relying on this library for HTTP/2 functionality become susceptible to denial-of-service attacks that can crash services or cause unexpected behavior. The vulnerability's exploitation potential increases when considering that HTTP/2 connections often maintain persistent streams, creating extended attack surfaces where idle stream handling becomes a critical point of failure. Attackers could leverage this vulnerability to cause service disruption, potentially affecting high-traffic websites, API endpoints, and enterprise applications that depend on HTTP/2 performance optimizations.
Security practitioners should prioritize immediate mitigation by upgrading to nghttp2 version 1.6.0 or later, where the heap-use-after-free issue has been resolved through proper memory management fixes. The vulnerability aligns with CWE-416, which specifically addresses use-after-free conditions, and demonstrates characteristics consistent with ATT&CK technique T1499.004 for network denial of service attacks. Organizations should implement comprehensive monitoring for abnormal connection behavior and memory access patterns that might indicate exploitation attempts. Additionally, the vulnerability highlights the importance of thorough testing of memory management code in high-performance networking libraries, particularly those handling persistent connections and stream lifecycle management. Regular security assessments of HTTP/2 implementations and dependency updates remain crucial for maintaining resilient infrastructure against such memory corruption vulnerabilities that can have cascading effects across interconnected systems.