CriticalCVE-2025-0994

    Trimble Cityworks Deserialization Vulnerability (CVE-2025-0994)

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

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    What is affected, what to do

    Trimble Cityworks versions prior to 15.8.9 and Cityworks with office companion versions prior to 23.10 are vulnerable to a deserialization vulnerability. This could allow an authenticated user to perform a remote code execution attack against a customer’s Microsoft Internet Information Services (IIS) web server.

    The vulnerability is being actively exploited; treat it as a priority. Update Trimble Cityworks to version 15.8.9, Trimble Cityworks (with office companion) to version 23.10. Immediate actions, mitigation and detection rules are in the runbook below.

    Affected
    • Trimble Cityworks lt *..15.8.9
    • Trimble Cityworks (with office companion) lt *..23.10
    Fixed in
    • Trimble Cityworks 15.8.9
    • Trimble Cityworks (with office companion) 23.10

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

    Metrics

    8.8

    Priority

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

    Source: NVD, CVSS v3

    8.8

    CVSS v3

    Severity High on the scale from 0 to 10.

    Source: pwn.watch, CVE.org, CISA ICS

    31.3 %

    EPSS score

    Elevated — model estimates 10-50% exploitation likelihood.

    Source: FIRST EPSS, percentile 98.3

    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
    228.95 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.

    Read in glossary
    8.8 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
    8.8
    CVSS v4

    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
    8.6
    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“.

    Read in glossary
    31.3 %
    Elevated — model estimates 10-50% exploitation likelihood.
    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.

    Read in glossary
    98.3
    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
    CISA assessment (SSVC)
    Exploitation: active · not automatable · Technical impact: total
    Source: CISA Vulnrichment, as of 15 August 2025
    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

    The flaw is network-reachable with low attack complexity. It needs only a low-privileged account and gives full code execution in the IIS server context. CISA does not flag ransomware use, but exploitation likelihood is very high. Cityworks is a GIS-centric asset management platform used mainly by municipalities and water/wastewater utilities. Attackers use it as a beachhead: they drop webshells, stage tooling, then pivot towards ArcGIS, database and potentially OT-adjacent systems. If you run Cityworks, and especially if it is internet-facing or in a KRITIS context, treat this as critical and patch or isolate within 24 h. Internal-only instances follow at high priority in the next maintenance window, together with a compromise assessment.

    1. Runbook step 1

      Immediate response (0-24 h)

      • Inventory: Identify every on-prem Cityworks instance, including Office Companion deployments, and check the version. Vulnerable releases are Cityworks < 15.8.9 and Cityworks with Office Companion < 23.10. Hosted (Cityworks Online) customers should get written confirmation of update status from the vendor.
      • Patch: Upgrade to Cityworks 15.8.9 or Office Companion 23.10. Internet-facing instances go first. Until patched, restrict IIS access by firewall to internal ranges or VPN only.
      • Check for compromise before patching: Take a snapshot or forensic image of the IIS host before upgrading. Then sweep webroot and the Cityworks directories for newly created .aspx, .ashx, .asmx or .dll files, and check for any child processes of w3wp.exe (see Detection).
      • Rotate credentials: Exploitation requires authentication. Reset passwords for any Cityworks users with anomalous logons. Also rotate the IIS app-pool identity, the database connection strings in web.config, and the ArcGIS/Esri service accounts that Cityworks uses.
      • If you find indicators: Isolate the server and trigger the IR process. Assess NIS2/national reporting obligations (24 h early warning), especially if you are a water, wastewater or municipal utility operator.

    2. Runbook step 2

      Mitigation layers

      • Network segmentation: Place the Cityworks IIS server in a dedicated DMZ or server zone. Allowlist its egress to the database, ArcGIS server and update sources only. This frustrates reverse shells and tool staging. The server must have no route into OT/SCADA networks.
      • IIS hardening: Make sure the app-pool identity has no local admin or domain admin rights. Use a dedicated least-privilege account (ApplicationPoolIdentity or gMSA) instead.
      • File system permissions: Move the Cityworks attachment directory outside wwwroot and limit it to read/write, with no execute. Give the app-pool identity read-only access to webroot. This blocks webshell drops.
      • WAF/reverse proxy: Publish Cityworks only through an authenticating reverse proxy with MFA (e.g. Entra ID Application Proxy). Log or block POST bodies that carry .NET serialization markers: Base64 prefix AAEAAAD///// (BinaryFormatter), JSON $type fields, and TypeConfuseDelegate/ObjectDataProvider strings.
      • IAM: Disable dormant and shared Cityworks accounts and time-box contractor access. Every valid account is a prerequisite for RCE here.
      • Endpoint: Run EDR on the IIS host in block mode. Add an ASR rule or AppLocker/WDAC policy that prevents w3wp.exe from launching script interpreters.

    3. Runbook step 3

      Detection rules

      • Process ancestry (Sysmon EID 1 / Security 4688): w3wp.exe spawning cmd.exe, powershell.exe, rundll32.exe, certutil.exe, bitsadmin.exe or whoami.exe. KQL: DeviceProcessEvents | where InitiatingProcessFileName =~ "w3wp.exe" and FileName in~ ("cmd.exe","powershell.exe","rundll32.exe","certutil.exe","whoami.exe")
      • Webshell drops (Sysmon EID 11): New .aspx, .ashx, .asmx, .config or .dll files written by w3wp.exe under inetpub, the Cityworks install path or the attachment directory. Sigma shape: Image|endswith: '\w3wp.exe' + TargetFilename|endswith: ['.aspx','.ashx','.asmx'].
      • IIS W3C logs: Watch for unusually large POSTs to Cityworks endpoints from unfamiliar source IPs. Also flag follow-up 200 responses on newly appearing .aspx paths, and first-seen logons for an account from foreign ASNs. SPL: index=iis cs_method=POST cs_uri_stem="*Cityworks*" | stats count by c_ip, cs_username | where count>50
      • Network telemetry (Zeek/Suricata): Look for outbound connections from the Cityworks host to unknown external destinations. Examples include HTTP downloads of .exe or .ps1 files, Cobalt Strike-style beaconing, and DNS lookups for newly registered domains.
      • Application logs: Check the Windows Application log for ASP.NET warnings (Event ID 1309/1316) that reference deserialization or ViewState errors. Also review Cityworks logons outside business hours.

    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

    Trimble Cityworks versions prior to 15.8.9 and Cityworks with office companion versions prior to 23.10 are vulnerable to a deserialization vulnerability. This could allow an authenticated user to perform a remote code execution attack against a customer’s Microsoft Internet Information Services (IIS) web server.

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

    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
    TrimbleCityworks
    • < 15.8.9
    • 15.8.9
    TrimbleCityworks (with office companion)
    • < 23.10
    • 23.10
    trimblecityworks
    • < 15.8.9
    • 23.0 – < 23.10
    • 15.8.9
    • 23.10

    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

    • cisa.govCISA guidance: Trimble Cityworksgovernment-resource, Third-party advisory, Third-party advisory, US government resource, pwn-watch
    • learn.assetlifecycle.trimble.comTrimble advisory: Trimble CityworksVendor advisory, Vendor advisory, pwn-watch
    • cisa.govknown-exploited-vulnerabilities-catalog?field_cve=CVE-2025-0994government-resource, US government resource
    • pwn.watchpwn.watch: Trimble Cityworks: Cityworks Deserialization Vulnerabilitypwn-watch
    • NVD (NIST)NVD: CVE-2025-0994pwn-watch
    • cisa.govCISA Known Exploited Vulnerabilities Catalogpwn-watch
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