CVE-2025-59050: greenshot Insecure Deserialization

Description

Greenshot is an open source Windows screenshot utility. Greenshot 1.3.300 and earlier deserializes attacker-controlled data received in a WM_COPYDATA message using BinaryFormatter.Deserialize without prior validation or authentication, allowing a local process at the same integrity level to trigger arbitrary code execution inside the Greenshot process. The vulnerable logic resides in a WinForms WndProc handler for WM_COPYDATA (message 74) that copies the supplied bytes into a MemoryStream and invokes BinaryFormatter.Deserialize, and only afterward checks whether the specified channel is authorized. Because the authorization check occurs after deserialization, any gadget chain embedded in the serialized payload executes regardless of channel membership. A local attacker who can send WM_COPYDATA to the Greenshot main window can achieve in-process code execution, which may aid evasion of application control policies by running payloads within the trusted, signed Greenshot.exe process. This issue is fixed in version 1.3.301. No known workarounds exist.

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CVSS v3.1 Score

8.4

HIGH

CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Weakness Type (CWE)

CWE-502 Deserialization of Untrusted Data

Affected Products

Vendor	Product	Versions
getgreenshot	greenshot	< 1.3.301

References

Advisories & Patches

https://github.com/greenshot/greenshot/commit/f5a29a2ed3b0eb49231c0f4618300f488cf1b04d https://github.com/greenshot/greenshot/security/advisories/GHSA-8f7f-x7ww-xx5w https://github.com/greenshot/greenshot/security/advisories/GHSA-8f7f-x7ww-xx5w

Exploits

https://github.com/greenshot/greenshot/security/advisories/GHSA-8f7f-x7ww-xx5w https://github.com/greenshot/greenshot/security/advisories/GHSA-8f7f-x7ww-xx5w

Frequently Asked Questions

What is CVE-2025-59050? +

Greenshot is an open source Windows screenshot utility. Greenshot 1.3.300 and earlier deserializes attacker-controlled data received in a WM_COPYDATA message using BinaryFormatter.Deserialize without prior validation or authentication, allowing a local process at the same integrity level to trigger arbitrary code execution inside the Greenshot process. The vulnerable logic resides in a WinForms WndProc handler for WM_COPYDATA (message 74) that copies the supplied bytes into a MemoryStream and invokes BinaryFormatter.Deserialize, and only afterward checks whether the specified channel is authorized. Because the authorization check occurs after deserialization, any gadget chain embedded in the serialized payload executes regardless of channel membership. A local attacker who can send WM_COPYDATA to the Greenshot main window can achieve in-process code execution, which may aid evasion of application control policies by running payloads within the trusted, signed Greenshot.exe process. This issue is fixed in version 1.3.301. No known workarounds exist. It has a CVSS v3.1 base score of 8.4 (HIGH).

How severe is CVE-2025-59050? +

CVE-2025-59050 has a CVSS v3.1 score of 8.4 out of 10, rated HIGH. This is a high-severity vulnerability that should be prioritized for patching.

What products are affected by CVE-2025-59050? +

CVE-2025-59050 affects products from getgreenshot, specifically: greenshot. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2025-59050? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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