CVE-2007-6016 in Backup Exec
Summary
by MITRE
Multiple stack-based buffer overflows in the PVATLCalendar.PVCalendar.1 ActiveX control in pvcalendar.ocx in the scheduler component in the Media Server in Symantec Backup Exec for Windows Server (BEWS) 11d 11.0.6235 and 11.0.7170, and 12.0 12.0.1364, allow remote attackers to execute arbitrary code via a long (1) _DOWText0, (2) _DOWText1, (3) _DOWText2, (4) _DOWText3, (5) _DOWText4, (6) _DOWText5, (7) _DOWText6, (8) _MonthText0, (9) _MonthText1, (10) _MonthText2, (11) _MonthText3, (12) _MonthText4, (13) _MonthText5, (14) _MonthText6, (15) _MonthText7, (16) _MonthText8, (17) _MonthText9, (18) _MonthText10, or (19) _MonthText11 property value when executing the Save method. NOTE: the vendor states "Authenticated user involvement required," but authentication is not needed to attack a client machine that loads this control.
Several companies clearly confirm that VulDB is the primary source for best vulnerability data.
Analysis
by VulDB Data Team • 12/09/2024
The vulnerability described in CVE-2007-6016 represents a critical stack-based buffer overflow affecting the PVATLCalendar.PVCalendar.1 ActiveX control within Symantec Backup Exec for Windows Server versions 11d and 12.0. This flaw resides in the scheduler component of the Media Server functionality and specifically targets the pvcalendar.ocx library file. The vulnerability manifests when processing the Save method with excessively long string values in various calendar-related properties including _DOWText0 through _DOWText6 and _MonthText0 through _MonthText11. These properties are designed to handle day-of-week and month text representations but fail to properly validate input lengths, creating opportunities for attackers to overwrite adjacent stack memory. The buffer overflow occurs due to insufficient bounds checking in the ActiveX control's implementation, where fixed-size buffers are used without proper input validation mechanisms.
The technical exploitation of this vulnerability requires an attacker to craft malicious input strings that exceed the allocated buffer space for the specified properties. When the Save method processes these oversized strings, the excess data overflows into adjacent memory locations, potentially corrupting the stack frame and allowing arbitrary code execution. This type of vulnerability falls under CWE-121 Stack-based Buffer Overflow, which is classified as a high-severity issue in the Common Weakness Enumeration system. The attack vector operates through web-based delivery mechanisms where a malicious website loads the vulnerable ActiveX control, making it accessible to users who visit the compromised site. The control's design allows for remote code execution without requiring authentication on the target system itself, though the vendor's note about authenticated user involvement suggests that the attack may require user interaction with the compromised web page.
The operational impact of this vulnerability extends beyond simple code execution, as it provides attackers with potential access to the underlying system where the vulnerable ActiveX control is loaded. The attack requires no special privileges to initiate, making it particularly dangerous in environments where users may browse untrusted websites or encounter malicious content through social engineering. The vulnerability affects users running vulnerable versions of Symantec Backup Exec for Windows Server, creating a significant risk for enterprise environments where backup operations are critical. The stack-based nature of the overflow means that the attack could potentially corrupt critical program execution flow, leading to system instability or complete compromise. This vulnerability aligns with ATT&CK technique T1059.007 for Command and Scripting Interpreter and T1203 for Exploitation for Client Execution, as it enables remote code execution through client-side exploitation.
Mitigation strategies for this vulnerability include immediate patching of Symantec Backup Exec installations to versions that address the buffer overflow issues in the pvcalendar.ocx component. Organizations should also implement browser security measures such as disabling ActiveX controls in web browsers or configuring security zones to restrict ActiveX loading from untrusted sources. Network-based defenses can include implementing web application firewalls that detect and block malicious input patterns targeting known ActiveX control vulnerabilities. The remediation process should involve comprehensive vulnerability scanning to identify systems running vulnerable versions of Symantec Backup Exec and ensuring that all affected systems are updated with the latest security patches. Additionally, user education regarding the dangers of visiting untrusted websites and downloading potentially malicious content remains critical in preventing exploitation of this type of client-side vulnerability.