CVE-2026-30041: FastStone Image Viewer Integer Overflow – PSD Parser Code Execution Risk

Technical summary

CVE-2026-30041 is an integer overflow vulnerability in the PSD parser component of FastStone Image Viewer v8.3. The vulnerability is triggered when processing a maliciously crafted PSD file, causing uncontrolled memory access or allocation failure. The integer overflow occurs during file parsing, likely in size or offset calculations, allowing attackers to either exhaust system resources or corrupt heap memory structures. The CVSS 3.1 vector (AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H) reflects a network-exploitable condition requiring no privileges or user interaction, with high availability impact but no confidentiality or integrity impact in the base metrics.

Business impact

Organizations and individuals relying on FastStone Image Viewer v8.3 for image processing workflows face operational disruption through denial-of-service attacks. If code execution variants are discovered or developed, the impact escalates significantly—an attacker could gain execution privileges within the image viewer's process context, potentially leading to lateral movement, data exfiltration, or further system compromise. For businesses using FastStone in batch processing pipelines or handling untrusted image sources, this vulnerability introduces a critical supply-chain risk.

Affected systems

FastStone Image Viewer version 8.3 is affected. Confirm whether your organization is running this specific version or earlier versions that may contain the same flaw. Check deployment inventories, particularly in design teams, marketing departments, or any departments that routinely open image files from external sources.

Exploitability

The vulnerability requires an attacker to deliver a crafted PSD file to a victim. There is no requirement for user privileges or complex interaction beyond opening the file. Network-based delivery (email attachment, malicious website, file-sharing service) is feasible. No active exploit code is known to be publicly available at this time, and the vulnerability is not listed on CISA's Known Exploited Vulnerabilities (KEV) catalog. However, the straightforward attack vector and low complexity mean that exploit development is probable once proof-of-concept details circulate in security communities.

Remediation

Upgrade FastStone Image Viewer to a patched version released by the vendor after the vulnerability disclosure date. Pending patch availability or during rollout, implement application whitelisting or sandboxing for image processing operations. Restrict file-opening permissions for untrusted PSD sources, and educate users to avoid opening PSD files from suspicious origins. Consider temporarily disabling PSD support if feasible in your workflow.

Patch guidance

Monitor FastStone's official website and security advisories for an updated release addressing CVE-2026-30041. Vendor advisories typically provide specific patch version numbers and upgrade paths. Once a patch is released, prioritize deployment across all affected instances, particularly user workstations and automated image processing systems. Verify patch application through version checks and endpoint detection tools.

Detection guidance

Monitor for failed or crashed instances of FastStone Image Viewer, particularly when triggered by PSD file processing. Look for suspicious PSD files being delivered via email or downloaded from unusual sources. Endpoint detection and response (EDR) solutions can flag abnormal memory access patterns during image parsing. Log file access patterns to identify attempts to open PSD files with unusual characteristics (excessive file size, unusual headers, or suspicious metadata).

Why prioritize this

This vulnerability merits immediate attention due to its high CVSS score (7.5), network attack vector, and lack of user interaction requirement. While currently not on CISA's KEV list, the simplicity of triggering the flaw via a crafted file means remediation should not be deferred. Organizations should prioritize patching within 30 days, particularly if users frequently handle external image files.

Risk score, explained

The CVSS 3.1 score of 7.5 (HIGH) reflects the combination of network accessibility (AV:N), low attack complexity (AC:L), no privilege requirement (PR:N), no user interaction (UI:N), high availability impact (A:H), and isolated scope (S:U). The absence of confidentiality and integrity impact in the base metrics suggests the primary risk is denial of service; however, integer overflows can be weaponized for code execution under certain conditions, making this a credible high-risk vulnerability worthy of swift remediation despite not reaching CVSS critical territory.

Frequently asked questions