CVE-2025-59050: High Vulnerability in getgreenshot greenshot

This vulnerability allows local attackers to execute arbitrary code within the Greenshot process due to insecure deserialization of attacker-controlled data. Specifically, Greenshot versions 1.3.300 and earlier deserialize data received in a WM_COPYDATA message without adequate validation or authentication, leading to significant security risks. The CVSS score of 8.4 categorizes this issue as a high-severity vulnerability, underscoring the urgency for organizations to address it.

The risk to organizations includes potential unauthorized access and execution of malicious payloads, which could bypass application control policies. Local attackers with the ability to send WM_COPYDATA to Greenshot's main window can exploit this vulnerability effectively, resulting in in-process code execution.

This issue was published on September 16, 2025, and the urgency for defenders is critical. Organizations should prioritize patching immediately to prevent exploitation. The vulnerability has not been reported as actively exploited, but its potential impact makes it necessary for defenders to take swift action.

The remediation is straightforward as the issue is resolved in version 1.3.301 of Greenshot. Organizations using earlier versions must upgrade to mitigate this vulnerability effectively.

Vulnerability Details

Greenshot is an open source Windows screenshot utility. The vulnerability arises from the use of BinaryFormatter.Deserialize without prior validation or authentication. This allows a local process at the same integrity level to trigger arbitrary code execution inside the Greenshot process. The vulnerable logic is located in a WinForms WndProc handler for WM_COPYDATA, where the supplied bytes are copied into a MemoryStream and deserialized before checking channel authorization.

The CVSS score is 8.4, indicating a high severity level due to its local attack vector, low complexity, and high impact on confidentiality, integrity, and availability.

Affected products include Greenshot, specifically versions prior to 1.3.301. The Common Weakness Enumeration (CWE) classification for this vulnerability is CWE-502, which pertains to deserialization of untrusted data.

Technical Analysis

The root cause of this vulnerability is the insecure deserialization process that occurs in Greenshot. A local attacker can manipulate the WM_COPYDATA message to send crafted data to the Greenshot application, which will then be deserialized without proper checks. The attack vector is local, meaning physical or local access to the machine is required to exploit this vulnerability.

The attack complexity is low, as no special conditions or high-level privileges are required to exploit this vulnerability. Furthermore, user interaction is not needed, making it easier for attackers to execute the attack. Once the crafted message is sent, the payload is executed within the context of the Greenshot application, thereby taking advantage of the trusted execution environment.

The impacts of this vulnerability are severe, with high confidentiality, integrity, and availability impacts. Successful exploitation of this vulnerability allows attackers to run arbitrary code within the Greenshot process, which may lead to further compromise of the system.

Risk & Impact Analysis

Real-world deployment risk associated with this vulnerability is significant. Organizations that utilize Greenshot in sensitive environments may face potential data breaches or unauthorized access due to this vulnerability. The blast radius could be extensive, as any local user with the ability to send WM_COPYDATA messages can exploit this vulnerability, which could lead to widespread impacts within the organization.

The urgency assessment based on the CVSS score of 8.4 indicates that organizations should address this vulnerability in their priority patch cycle. Given that no public exploits have been confirmed, the focus should still be on immediate remediation to prevent any potential exploitation.

Exploitation Status

Affected Versions

All versions prior to vendor patch, specifically Greenshot 1.3.300 and earlier, are affected by this vulnerability.

Mitigation & Remediation

Organizations should upgrade to Greenshot version 1.3.301 to remediate this vulnerability. Ensure that the latest security patches are applied to all installations. Additionally, implementing application control policies may help mitigate the risk of unauthorized processes running within trusted applications.

For further security practices, organizations may consider conducting a comprehensive security assessment, including application security assessments to identify potential vulnerabilities within their systems.

Detection Guidance

Monitoring for unusual WM_COPYDATA messages and logging any unauthorized access attempts to the Greenshot process will help identify potential exploitation attempts. Watch for behavioral anomalies that may indicate code execution within the Greenshot environment.

AppSecure Threat Intelligence Insight

The long-term significance of CVE-2025-59050 lies in its demonstration of the risks associated with insecure deserialization. Security teams should recognize this vulnerability as part of a broader trend in application security, reinforcing the need for rigorous input validation and secure coding practices.

Organizations should learn from this incident to enhance their security posture. Regular penetration testing, such as penetration testing services, can help identify and remediate vulnerabilities before they can be exploited.

Furthermore, security teams should stay informed about vulnerabilities and implement best practices for application security, including ongoing training and awareness programs.

In conclusion, CVE-2025-59050 serves as a reminder of the importance of secure coding practices. By prioritizing security, organizations can prevent similar vulnerabilities from impacting their systems.