CVE-2010-2629 in Ace 4710
Summary
by MITRE
The Cisco Content Services Switch (CSS) 11500 with software 8.20.4.02 and the Application Control Engine (ACE) 4710 with software A2(3.0) do not properly handle LF header terminators in situations where the GET line is terminated by CRLF, which allows remote attackers to conduct HTTP request smuggling attacks and possibly bypass intended header insertions via crafted header data, as demonstrated by an LF character between the ClientCert-Subject and ClientCert-Subject-CN headers. NOTE: this vulnerability exists because of an incomplete fix for CVE-2010-1576.
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Analysis
by VulDB Data Team • 01/04/2018
The vulnerability described in CVE-2010-2629 represents a critical HTTP request smuggling flaw affecting Cisco Content Services Switch models 11500 and Application Control Engine models 4710. This security weakness stems from improper handling of line feed (LF) header terminators when the GET line is terminated with carriage return line feed (CRLF) sequences, creating a dangerous inconsistency in HTTP protocol processing that adversaries can exploit to manipulate request parsing and potentially bypass security controls.
The technical flaw manifests when HTTP headers are processed by these Cisco devices, where the system fails to consistently normalize line terminators between different header sections. Specifically, when the GET line uses CRLF termination but subsequent headers contain LF terminators, the device's HTTP parser becomes confused about header boundaries, allowing attackers to inject malicious header content that gets parsed incorrectly. This inconsistency creates opportunities for HTTP request smuggling where crafted header data can be interpreted as part of the request body rather than header fields, effectively enabling attackers to craft requests that appear valid to the client but are processed differently by the server.
The operational impact of this vulnerability extends beyond simple request manipulation, as it can be leveraged to bypass intended security header insertions and potentially gain unauthorized access to protected resources. The vulnerability specifically demonstrates how an LF character between ClientCert-Subject and ClientCert-Subject-CN headers can be exploited, indicating that certificate-based authentication mechanisms may be compromised. This type of attack can enable man-in-the-middle scenarios where attackers can manipulate authentication flows, potentially allowing unauthorized certificate validation or bypassing certificate-based access controls entirely.
From a cybersecurity perspective, this vulnerability aligns with CWE-129 and CWE-134 categories related to improper handling of input boundaries and insecure handling of HTTP headers, while also mapping to ATT&CK techniques involving protocol manipulation and credential access. The incomplete fix for CVE-2010-1576 suggests that Cisco's initial response to similar issues was insufficient, leaving the system vulnerable to more sophisticated exploitation patterns. This represents a classic case of protocol normalization failure in web application firewalls where inconsistent handling of line terminators creates attack vectors that can be systematically exploited.
The remediation approach requires immediate deployment of updated firmware versions that properly normalize header terminators and implement consistent HTTP parsing rules across all header sections. Organizations should also implement network segmentation and additional monitoring to detect anomalous header patterns that might indicate exploitation attempts. Security teams must verify that their monitoring tools can detect HTTP smuggling patterns and that access controls are properly enforced even when header parsing inconsistencies occur. The vulnerability demonstrates the critical importance of thorough testing for protocol handling edge cases and the necessity of complete fixes rather than partial solutions to prevent similar issues from persisting in network security infrastructure.