CVE-2018-21245 in Pound
Summary
by MITRE
Pound before 2.8 allows HTTP request smuggling, a related issue to CVE-2016-10711.
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Analysis
by VulDB Data Team • 06/16/2020
CVE-2018-21245 represents a critical HTTP request smuggling vulnerability affecting Pound proxy versions prior to 2.8. This vulnerability stems from improper handling of HTTP request parsing and normalization within the proxy server's processing pipeline. The flaw allows attackers to manipulate HTTP request boundaries and headers in ways that can bypass security controls, potentially leading to unauthorized access or data exposure. The vulnerability is particularly concerning as it operates at the HTTP protocol level, where subtle parsing differences can create exploitable conditions between the client and backend servers.
The technical implementation of this vulnerability involves the proxy's failure to properly normalize HTTP request data during processing. When Pound receives HTTP requests, it does not consistently handle header fields, line endings, or request boundaries in a manner that prevents attackers from crafting requests that appear valid to the proxy but are interpreted differently by backend servers. This inconsistency creates a window where malicious actors can inject or modify request components that get processed differently downstream. The vulnerability specifically relates to how the proxy handles header concatenation, folding, and encoding variations that are permitted under HTTP specifications but can be exploited when not properly normalized.
From an operational impact perspective, this vulnerability enables several attack vectors including cache poisoning, session hijacking, and cross-site request forgery exploitation. Attackers can manipulate the proxy's request processing to cause backend servers to interpret requests differently than intended, potentially allowing them to access restricted resources or bypass authentication mechanisms. The vulnerability's relationship to CVE-2016-10711 indicates a pattern of parsing inconsistencies that have persisted across multiple versions, suggesting this may be a systemic architectural issue rather than an isolated bug. Organizations using Pound proxy servers without proper mitigation measures face significant risk of unauthorized data access and potential service disruption.
Security mitigations for CVE-2018-21245 primarily involve upgrading to Pound version 2.8 or later, which includes proper HTTP request normalization and validation. Additionally, implementing strict HTTP header validation policies, enabling comprehensive logging of HTTP requests, and deploying web application firewalls can provide additional defense layers. Organizations should also consider implementing proper request boundary checking and ensuring consistent header handling across all HTTP processing components. The vulnerability aligns with CWE-444, which addresses improper HTTP request handling, and maps to ATT&CK technique T1190 for exploiting vulnerabilities in proxy services. Regular security assessments of proxy configurations and thorough testing of HTTP request handling mechanisms should be conducted to prevent exploitation of similar parsing inconsistencies that may exist in other components of the network infrastructure.