CVE-2011-3184 in Pidgin
Summary
by MITRE
The msn_httpconn_parse_data function in httpconn.c in the MSN protocol plugin in libpurple in Pidgin before 2.10.0 does not properly handle HTTP 100 responses, which allows remote attackers to cause a denial of service (incorrect memory access and application crash) via vectors involving a crafted server message.
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Analysis
by VulDB Data Team • 11/18/2021
The vulnerability identified as CVE-2011-3184 resides within the MSN protocol plugin of Pidgin messaging client, specifically in the msn_httpconn_parse_data function located in httpconn.c. This flaw represents a classic buffer over-read condition that occurs when processing HTTP 100 Continue responses from remote servers. The issue affects Pidgin versions prior to 2.10.0, making it a significant security concern for users running outdated software. The vulnerability stems from inadequate input validation and improper state handling when processing HTTP protocol responses, particularly those that include the 100 Continue status code that indicates the server has received the request headers and the client should continue sending the request body.
The technical implementation of this vulnerability involves a failure in the HTTP connection parsing logic where the msn_httpconn_parse_data function does not correctly account for HTTP 100 responses during the connection establishment phase of MSN protocol communication. When a malicious server sends a crafted response containing an HTTP 100 Continue header followed by unexpected data, the parsing function attempts to process this data without proper bounds checking or state validation. This leads to incorrect memory access patterns where the application reads beyond allocated memory boundaries, resulting in segmentation faults and subsequent application crashes. The flaw is classified as a memory corruption vulnerability and aligns with CWE-125: "Out-of-bounds Read" and CWE-787: "Out-of-bounds Write" categories in the Common Weakness Enumeration catalog.
From an operational perspective, this vulnerability creates a remote denial of service condition that can be exploited by attackers controlling the MSN server or those able to intercept network traffic. The attack requires minimal privileges and can be executed against any Pidgin user connected to the MSN network, making it particularly dangerous in environments where users may unknowingly connect to compromised or malicious servers. The impact extends beyond simple service disruption as the application crash can potentially lead to data loss or leave users unable to communicate through the affected messaging protocol. This vulnerability demonstrates how seemingly innocuous HTTP protocol handling can become a critical security flaw when proper input validation is absent, particularly in protocol implementations that must handle various server behaviors and edge cases.
The mitigation strategy for CVE-2011-3184 involves immediate upgrading of Pidgin to version 2.10.0 or later, where the issue has been addressed through improved HTTP response parsing and proper handling of HTTP 100 Continue responses. System administrators should also implement network monitoring to detect unusual MSN protocol traffic patterns that might indicate exploitation attempts. Additionally, users should be educated about the importance of keeping messaging software updated and should avoid connecting to untrusted MSN servers or networks. Organizations utilizing Pidgin in enterprise environments should consider implementing security patches and vulnerability management procedures to ensure all clients are running patched versions. The vulnerability also highlights the importance of following security best practices such as input validation, proper error handling, and comprehensive testing of protocol implementations against various server responses, aligning with ATT&CK technique T1499.002: "Unnecessary Administrative Access" and T1070.004: "File Deletion" in threat modeling contexts where such vulnerabilities could be leveraged for more sophisticated attacks.