CVE-2015-3249 in Traffic Server
Summary
by MITRE
The HTTP/2 experimental feature in Apache Traffic Server 5.3.x before 5.3.1 allows remote attackers to cause a denial of service (out-of-bounds access and daemon crash) or possibly execute arbitrary code via vectors related to the (1) frame_handlers array or (2) set_dynamic_table_size function.
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Analysis
by VulDB Data Team • 01/21/2021
The vulnerability identified as CVE-2015-3249 represents a critical security flaw within Apache Traffic Server's experimental HTTP/2 implementation. This issue affects versions 5.3.x prior to 5.3.1 and demonstrates the inherent risks associated with experimental features that may not undergo the same rigorous security testing as core functionalities. The vulnerability stems from improper bounds checking and memory management within the HTTP/2 protocol handling mechanisms, creating potential pathways for remote exploitation that could compromise system integrity and availability.
The technical exploitation occurs through two primary vectors that demonstrate different aspects of the underlying memory corruption issues. The first vector involves the frame_handlers array, which suggests improper bounds checking when processing HTTP/2 frames, potentially allowing attackers to access memory locations beyond the allocated array boundaries. This type of out-of-bounds access commonly leads to undefined behavior and can be leveraged to trigger daemon crashes or potentially execute arbitrary code. The second vector targets the set_dynamic_table_size function, indicating that dynamic table management within the HTTP/2 implementation contains vulnerabilities that could be exploited through carefully crafted inputs.
This vulnerability directly maps to CWE-125, which describes out-of-bounds read conditions, and CWE-787, which covers out-of-bounds write conditions, both of which are fundamental memory safety issues that can lead to denial of service or code execution. The operational impact of this vulnerability extends beyond simple service disruption, as it can potentially allow remote attackers to gain unauthorized code execution privileges on the affected server. The daemon crash scenario represents a denial of service condition that could be exploited repeatedly to maintain system unavailability, while the arbitrary code execution possibility presents a more severe threat to system security and data integrity.
The attack surface for this vulnerability is particularly concerning given that HTTP/2 support in Apache Traffic Server was still experimental at the time of discovery. This highlights the importance of proper security validation for experimental features before deployment in production environments. Organizations using Apache Traffic Server with HTTP/2 enabled should immediately implement mitigations, including upgrading to version 5.3.1 or later where the vulnerability has been addressed. The vulnerability also underscores the need for comprehensive input validation and bounds checking in protocol implementations, particularly when handling variable-length data structures such as those used in HTTP/2 frame handling and dynamic table management.
From a threat modeling perspective, this vulnerability aligns with ATT&CK technique T1499.004, which covers network denial of service, and potentially T1059.007 for remote code execution if the arbitrary code execution vector is successfully exploited. The vulnerability demonstrates how experimental protocol support can introduce unexpected security risks, particularly when developers may not have fully considered all edge cases in memory management and input handling. Security teams should monitor their Apache Traffic Server deployments for any instances of HTTP/2 functionality and ensure immediate patching to prevent exploitation. The incident serves as a reminder of the critical importance of thorough security testing for all protocol implementations, especially those that handle network traffic and user input directly.