CVE-2017-8807 in Cache
Summary
by MITRE
vbf_stp_error in bin/varnishd/cache/cache_fetch.c in Varnish HTTP Cache 4.1.x before 4.1.9 and 5.x before 5.2.1 allows remote attackers to obtain sensitive information from process memory because a VFP_GetStorage buffer is larger than intended in certain circumstances involving -sfile Stevedore transient objects.
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Analysis
by VulDB Data Team • 01/10/2023
The vulnerability identified as CVE-2017-8807 represents a critical information disclosure flaw within Varnish HTTP Cache software versions 4.1.x prior to 4.1.9 and 5.x prior to 5.2.1. This issue stems from improper memory management in the cache_fetch.c source file where the vbf_stp_error function handles storage allocation for VFP_GetStorage buffers. The flaw specifically manifests when using the -sfile Stevedore transient objects, creating a scenario where buffer sizes exceed their intended dimensions under certain conditions.
The technical root cause of this vulnerability lies in the improper handling of memory allocation boundaries within the Varnish cache daemon's fetch process. When processing HTTP requests through the -sfile storage mechanism, the system allocates a buffer that becomes larger than expected due to miscalculations in memory boundary checks. This oversized buffer allocation creates a situation where adjacent memory segments containing sensitive data may be inadvertently exposed to remote attackers who can read beyond the intended buffer limits. The vulnerability operates at the intersection of memory management and network protocol handling, making it particularly dangerous in production environments where sensitive information might be cached.
From an operational impact perspective, this vulnerability allows remote attackers to extract sensitive information from process memory, potentially including authentication tokens, session data, user credentials, or other confidential information stored in the cache. The attack vector requires no authentication and can be executed from any remote location capable of sending HTTP requests to the vulnerable Varnish instance. The exposure of process memory contents can lead to privilege escalation, session hijacking, or complete system compromise depending on what sensitive data is cached. This vulnerability directly impacts the confidentiality aspect of the CIA triad and can result in significant data breaches when exploited in real-world scenarios.
The vulnerability aligns with CWE-200 (Information Exposure) and can be mapped to ATT&CK technique T1005 (Data from Local System) and T1041 (Exfiltration Over Command and Control Channel). Organizations using Varnish Cache in production environments should immediately implement mitigations including updating to patched versions 4.1.9 or 5.2.1, implementing network segmentation to limit exposure, and monitoring for anomalous memory access patterns. Additional protective measures include configuring proper access controls on cache storage directories, implementing network intrusion detection systems, and conducting regular security assessments of caching infrastructure. The vulnerability demonstrates the critical importance of proper memory boundary checking in high-performance caching systems where multiple concurrent processes access shared memory resources.