CriticalCVE-2025-40551

    SolarWinds Web Help Desk Deserialization of Untrusted Data Remote Code Execution Vulnerability (CVE-2025-40551)

    Published In CISA KEV since Sources: CVE.org, pwn.watch

    What is affected, what to do

    SolarWinds Web Help Desk was found to be susceptible to an untrusted data deserialization vulnerability that could lead to remote code execution, which would allow an attacker to run commands on the host machine. This could be exploited without authentication.

    The vulnerability is being actively exploited; treat it as a priority. Update web_help_desk to version 2026.1. Immediate actions, mitigation and detection rules are in the runbook below.

    Affected
    • SolarWinds Web Help Desk eq 12.8.8 HF1 and below..12.8.8 HF1 and below

    Not sure whether and how you are affected? Ask a question about this vulnerability

    Metrics

    9.8

    Priority

    XIEM Effective CVSS: highest available CVSS rating from NVD and vendor data.

    Source: NVD, CVSS v3

    9.8

    CVSS v3

    Severity Critical on the scale from 0 to 10.

    Source: CVE.org, pwn.watch

    84.2 %

    EPSS score

    High — model estimates ≥ 50% chance of real-world exploitation within 30 days.

    Source: FIRST EPSS, percentile 99.70

    Show all metrics
    Severity
    Critical
    Priority (0–325)

    The priority score is a consolidated metric that condenses several individual signals into a single, action-guiding ranking: technical severity (CVSS), exploitation likelihood (EPSS), known-exploited status (KEV) and the context of the affected asset. The aim is to answer the only truly important question in vulnerability management: what first?

    Read in glossary
    242.49 Methodology
    Exploit maturity

    An exploit is code or a technique that specifically uses a concrete vulnerability to force unintended behaviour — such as executing code or escalating privileges. It is the tool that turns a theoretical flaw into a practical attack.

    Read in glossary
    actively exploitedSource: VulnCheck KEV (opens in a new tab) How we classify
    XIEM Effective CVSS

    XIEM® is the tiered managed-security operating model from NEOSEC and a registered trademark of NEOSEC GmbH. It extends classic SIEM — the central collection, normalisation and correlation of security-relevant events — with endpoint forensics, network visibility and deception technology, and consolidates them into three building tiers: Sentry, Orchestrate and Command.

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    9.8 Methodology
    CVSS v3

    CVSS is the globally established, open standard for assessing the technical severity of a vulnerability on a scale from 0 to 10. It describes how easily a flaw can be exploited and what damage it can cause — but not how likely its actual exploitation is. CVSS and the complementary EPSS deliberately answer different questions.

    Read in glossary
    9.8
    EPSS score

    The EPSS score is the absolute model output for an individual vulnerability: the estimated probability of real-world exploitation within the next 30 days, expressed as a value between 0 and 1 (i.e. 0 % to 100 %). A score of 0.42 means „the model estimates a 42 % chance of real-world exploitation within 30 days“.

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    84.2 %
    High — model estimates ≥ 50% chance of real-world exploitation within 30 days.
    EPSS percentile

    The EPSS percentile is the relative position of a vulnerability within all EPSS-scored CVEs, expressed as a value between 0 and 1. A percentile of 0.90 means „this CVE has a higher EPSS score than 90 % of all other scored CVEs“. Unlike the EPSS score, it is not a probability — but a positioning within a ranking.

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    99.70
    Critical — this CVE ranks in the top fifth of all CVEs scored today (rank ≥ 80%).
    KEV status

    The KEV catalogue is a list maintained by the US authority CISA of vulnerabilities for which active exploitation in the wild has been confirmed. It answers not the question „how severe?“ but „is it already being attacked?“ — thereby sharply prioritising patching.

    Read in glossary
    Actively exploited
    Published
    In CISA KEV since

    The KEV catalogue is a list maintained by the US authority CISA of vulnerabilities for which active exploitation in the wild has been confirmed. It answers not the question „how severe?“ but „is it already being attacked?“ — thereby sharply prioritising patching.

    Read in glossary
    CWE

    CWE is a catalogue of typical weakness types in software and hardware — such as flawed input validation, unsafe memory handling or poor authentication. Where a CVE names a concrete vulnerability in a concrete product, a CWE describes the underlying class of defect.

    Read in glossary
    CWE-502

    Response and mitigation

    Why act now?

    Prioritisation rationale

    This flaw is reachable over the network with no authentication and no user interaction. It yields direct code execution on the host and sits among the CVEs most likely to be exploited. Web Help Desk has a track record of exploited deserialisation bugs. Attackers target it as an initial-access foothold because it is often internet-facing and holds privileged AD, mail and database credentials. CISA does not currently flag ransomware use, but WHD-based initial access is a classic precursor to it. Treat internet-exposed instances as an emergency and check NIS2 reporting obligations if you find a compromise. Internal-only instances should be patched as high priority within days.

    1. Runbook step 1

      Immediate response (0-24 h)

      • Inventory: Identify every SolarWinds Web Help Desk (WHD) instance, including forgotten test and legacy servers. All versions up to and including 12.8.8 HF1 are affected. Confirm the version via the admin console or the install files.
      • Patch: Upgrade to Web Help Desk 2026.1, the fixed release per the vendor. Start with internet-facing instances, then move to internally reachable ones.
      • Cut exposure now: If you cannot upgrade within hours, block internet access to WHD at the perimeter firewall or reverse proxy. Cover both the web and admin ports (commonly 8443/8081 — verify your actual configuration). Allow access only via VPN or an IP allowlist.
      • Compromise assessment before patching: Preserve logs, the WHD install directory and the running process list before upgrading. If you find signs of exploitation, isolate the host rather than just patching it.
      • Rotate credentials: WHD typically stores service accounts for LDAP/Active Directory, the database and mailboxes (IMAP/SMTP), plus API tokens for integrated systems. Rotate all of them on any exposed or suspicious instance.

    2. Runbook step 2

      Mitigation layers

      • Network segmentation: Place WHD servers in a dedicated DMZ or application zone. Apply default-deny egress, allowing only the database, mail server, LDAP and update destinations. This hampers reverse shells and second-stage payload downloads after successful deserialisation.
      • WAF/IPS: Block or alert on HTTP requests to WHD that carry serialised Java objects. Look for the magic bytes AC ED 00 05 in bodies, or Base64 rO0AB in parameters, headers or cookies. Add a Suricata rule with content:"rO0AB"; http_client_body; scoped to the WHD destination ports.
      • Reverse proxy path allowlist: Publish only the end-user paths that are actually required. Restrict admin and Ajax endpoints to admin networks. The context does not name the specific vulnerable endpoints — check the vendor advisory.
      • Endpoint hardening: Run the WHD service under a dedicated, unprivileged service account, not LocalSystem or root. Use an EDR or AppLocker rule to stop the WHD Java process from spawning shells (cmd.exe, powershell.exe, /bin/sh, bash).
      • IAM/least privilege: Reduce the AD bind accounts configured in WHD to read-only. Scope database accounts to the WHD schema only. This limits lateral movement after a compromise.

    3. Runbook step 3

      Detection rules

      • Process ancestry (Sysmon EID 1 / EDR): The WHD Java process spawning interpreters or recon tools. Sigma shape: ParentImage|endswith: '\java.exe' AND ParentCommandLine|contains: 'WebHelpDesk' AND Image|endswith: ['\cmd.exe','\powershell.exe','\whoami.exe','\certutil.exe','\rundll32.exe'].
      • Linux auditd: execve events whose ppid is the WHD Java process and whose exe is /bin/sh, /bin/bash, /usr/bin/curl or /usr/bin/wget. SPL: index=linux type=EXECVE parent_exe="*java*" (exe="/bin/sh" OR exe="/usr/bin/curl").
      • Web access logs: POST requests from external IPs with unusually large bodies or Base64 blobs containing rO0AB. Also flag bursts of HTTP 500 responses on Ajax or proxy endpoints when the same source IP has no prior successful login.
      • File system (Sysmon EID 11): New .jsp, .class or .jar files in the WHD install or webapp directories outside change windows point to web shells or persistence.
      • Network (Zeek/Sysmon EID 3): Outbound connections from the WHD host to unknown external IPs, especially right after inbound requests from internet sources. KQL: DeviceNetworkEvents | where InitiatingProcessFileName =~ "java.exe" and RemoteIPType == "Public" and DeviceName in (whd_hosts).

    Detection rules

    No NEOSEC detection rule is available for this vulnerability yet.

    Classification under NIS2 and CRA

    Rule-based classification from exploitation status and severity. It does not replace a case-by-case assessment.

    NIS2

    NIS2 is EU Directive (EU) 2022/2555 to raise the level of cybersecurity across the Union. It substantially broadens obligations compared with the first NIS directive: more sectors, mandatory risk management, staged reporting duties and personal accountability of senior management.

    Read in glossary
    Actively exploited: treat the vulnerability as a priority in vulnerability handling under Art. 21(2)(e) NIS2. If it is exploited in your environment, check the reporting obligation under Art. 23 (early warning within 24 hours).
    CRA

    The CRA is EU Regulation (EU) 2024/2847 setting horizontal cybersecurity requirements for „products with digital elements“ — from industrial controllers and software to connected consumer devices. For the first time manufacturers must ensure security across the entire product lifecycle, handle vulnerabilities and provide security updates.

    Read in glossary
    Since 11.09.2026, manufacturers of affected products with digital elements must report actively exploited vulnerabilities under Art. 14 CRA, with an early warning within 24 hours via ENISA's single reporting platform.
    ISO/IEC 27001

    ISO/IEC 27001 is the internationally leading standard for an information security management system (ISMS). It describes a risk-based, process-oriented framework to systematically plan, implement, review and improve information security.

    Read in glossary
    Control A.8.8, management of technical vulnerabilities: assess relevance to your systems, plan remediation and keep evidence.

    Description

    SolarWinds Web Help Desk was found to be susceptible to an untrusted data deserialization vulnerability that could lead to remote code execution, which would allow an attacker to run commands on the host machine. This could be exploited without authentication.

    Source: NVD (NIST), cvelistv5, CISA KEV Catalog, CVE.org (MITRE), pwn.watch

    Affected products

    The following versions are affected. Older releases of the same product line are also vulnerable unless stated otherwise.

    Affected products
    Affected versionsFixed in
    SolarWindsWeb Help Desk
    • 12.8.8 HF1 and below
    • —
    solarwindsweb_help_desk
    • < 2026.1
    • 2026.1

    Vendors and products

    Weakness classes (CWE)

    • CWE-502Deserialization of Untrusted Data

      Base

      The product deserializes untrusted data without sufficiently ensuring that the resulting data will be valid.

      Entry at MITRE CWE-502

    Public exploit references

    Publicly reported proof-of-concepts, exploit modules and detection templates for this vulnerability. NEOSEC links to the original sources only and does not provide any exploit code.

    Public exploit references
    CISA KEV CatalogCISA Known Exploited Vulnerability (opens in a new tab)cisa.govactively exploited

    References & sources

    • solarwinds.comSolarWinds Web Help Desk — CVE-2025-40551Vendor advisory, Patch, Vendor advisory, pwn-watch
    • documentation.solarwinds.comen/success_center/whd/content/release_notes/whd_2026-1_release_…Release notes, Release notes
    • cisa.govknown-exploited-vulnerabilities-catalog?field_cve=CVE-2025-40551government-resource, US government resource
    • pwn.watchpwn.watch: SolarWinds Web Help Desk: SolarWinds Web Help Desk Deserialization of Untrusted Data Vulnerabilitypwn-watch
    • NVD (NIST)NVD: CVE-2025-40551pwn-watch
    • cisa.govCISA Known Exploited Vulnerabilities Catalogpwn-watch
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