Raw vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:HSummary
CVE-2025-26399 is a critical-severity Deserialization of Untrusted Data (CWE-502) vulnerability in Solarwinds Web Help Desk. Its CVSS base score is 9.8 (Critical).
Operationally, exploitation aligns with the MITRE ATT&CK technique Exploit Public-Facing Application (T1190); ranked in the top 0.2% of CVEs by exploit likelihood; CISA has added it to the Known Exploited Vulnerabilities catalog.
The strongest mitigations our analysis identified map to SA-11 (Developer Testing and Evaluation) and SI-10 (Information Input Validation) — see the control section below for these in your framework.
Deeper analysis AI-assisted summary
Synthesised by an AI model from the NVD description and linked references — a reading aid, not an authoritative source.
SolarWinds Web Help Desk contains an unauthenticated AjaxProxy deserialization remote code execution vulnerability tracked as CVE-2025-26399. The flaw stems from improper handling of serialized data under CWE-502 and affects the web application component that processes AjaxProxy requests. It carries a CVSS 3.1 score of 9.8 and is explicitly described as a patch bypass for the earlier issues CVE-2024-28988 and CVE-2024-28986.
An attacker with no credentials or user interaction can send a crafted request over the network to trigger deserialization and execute arbitrary commands on the underlying host. Successful exploitation grants full control over the affected system, including the ability to read, modify, or delete data and to pivot further within the environment.
SolarWinds has released hotfix 1 for version 12.8.7, documented in the corresponding release notes and security advisory, to address the issue. CISA lists the vulnerability in its Known Exploited Vulnerabilities catalog, indicating that federal agencies must apply mitigations according to the published timelines.
Active exploitation of the vulnerability has been observed in the wild, as detailed in reporting from Microsoft. The EPSS score reached a peak of 0.3422 with a current value of 0.3053, reflecting sustained interest following disclosure.
OWASP Top 10 for Web (2025)
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2025-30842
Vulnerability Data
SolarWinds Web Help Desk was found to be susceptible to an unauthenticated AjaxProxy deserialization remote code execution vulnerability that, if exploited, would allow an attacker to run commands on the host machine. This vulnerability is a patch bypass of CVE-2024-28988,…
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which in turn is a patch bypass of CVE-2024-28986.
- CWE(s)
- KEV Date Added
- 09 March 2026
Related Threats
MITRE ATT&CK Enterprise Techniques
CVEs Like This One
Affected Assets
Mitigating Controls
Mitigating Controls (NIST 800-53 r5) AI
Developer testing and evaluation can uncover deserialization flaws before deployment.
Input validation directly stops deserialization of untrusted data by ensuring inputs are valid before processing.
Engineering principles such as safe deserialization and input sanitization structurally prevent the weakness from being introduced.
Integrity verification tools can detect malformed or tampered serialized data after the fact.
Mitigating Controls (NIST CSF 2.0) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.
PR.PS-02 addresses only post-deployment updates/patching and cannot prevent introduction of unsafe deserialization code, yet it can remediate some instances when the flaw exists in outdated libraries or components.
Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.
Security testing includes validation of deserialization routines and the use of untrusted data, reducing the likelihood that unsafe object reconstruction will be deployed.
Requiring vetted libraries, regular updates and SAST before release reduces the likelihood that deserialization logic will accept and act on attacker-controlled serialized objects.
Regular scanning of third-party libraries and timely patching reduce the likelihood that unsafe deserialization vulnerabilities remain active.
Mandatory malware scanning of data received over networks or storage media intercepts malicious serialized payloads before they are deserialized by the target application.