CVE-2007-2958 in Sylpheed
Summary
by MITRE
Format string vulnerability in the inc_put_error function in src/inc.c in Sylpheed 2.4.4, and Sylpheed-Claws (Claws Mail) 1.9.100 and 2.10.0, allows remote POP3 servers to execute arbitrary code via format string specifiers in crafted replies.
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Analysis
by VulDB Data Team • 07/21/2021
The vulnerability identified as CVE-2007-2958 represents a critical format string flaw in the Sylpheed email client and its Claws Mail derivative versions. This security weakness resides within the inc_put_error function located in the src/inc.c source file, specifically affecting Sylpheed versions up to 2.4.4 and Claws Mail versions 1.9.100 and 2.10.0. The flaw stems from improper handling of user-supplied data during error message generation, creating a path for remote code execution through crafted POP3 server responses. This vulnerability demonstrates the classic dangers of format string vulnerabilities where attacker-controlled input is directly passed to printf-like functions without proper sanitization.
The technical exploitation of this vulnerability occurs when a malicious POP3 server crafts specially formatted replies that contain format specifiers such as %s, %d, or %x within error messages. When the vulnerable Sylpheed or Claws Mail client processes these crafted responses through the inc_put_error function, the format string vulnerability allows the attacker to manipulate the stack contents and potentially execute arbitrary code with the privileges of the running email client process. This type of vulnerability falls under CWE-134 which specifically addresses the use of format strings with user-supplied data, making it particularly dangerous in networked applications where untrusted data sources are common. The vulnerability's impact is amplified by the fact that email clients typically run with elevated privileges and have access to sensitive user data.
The operational consequences of this vulnerability extend beyond simple remote code execution to encompass complete system compromise when attackers leverage the flaw in conjunction with other attack vectors. An attacker controlling a POP3 server can craft malicious error messages that overwrite critical program memory locations, potentially redirecting execution flow to malicious payloads. The vulnerability affects email clients that process POP3 protocol responses, making it particularly concerning for users who frequently access email through potentially compromised mail servers. This type of attack aligns with ATT&CK technique T1059.007 for command and scripting interpreter, where attackers can execute code remotely through manipulated input processing. The attack surface is further expanded by the fact that these email clients often maintain persistent connections and may be running in environments with elevated privileges, increasing the potential impact of successful exploitation.
Mitigation strategies for CVE-2007-2958 require immediate patching of affected Sylpheed and Claws Mail installations to versions that properly sanitize format string inputs. System administrators should implement network segmentation and firewall rules to restrict access to POP3 servers, particularly when dealing with untrusted or legacy mail infrastructure. The recommended approach involves updating to patched versions of the software, which typically include proper input validation and the use of secure printf alternatives such as snprintf instead of sprintf. Additionally, network monitoring should be enhanced to detect suspicious POP3 server behavior and malformed error messages that could indicate exploitation attempts. Organizations should also consider implementing email filtering solutions that can identify and block malformed POP3 responses before they reach vulnerable client applications. The vulnerability serves as a reminder of the critical importance of input validation in networked applications and the potential for remote code execution through seemingly benign error handling mechanisms.