CriticalCVE-2021-42258

    BQE BillQuick Web Suite SQL Injection Vulnerability (CVE-2021-42258)

    Published In CISA KEV since Sources: CVE.org

    What is affected, what to do

    The CVE-2021-42258 vulnerability in BQE BillQuick Web Suite allows for unauthenticated remote code execution via SQL injection. Attackers can execute arbitrary code by manipulating the txtID parameter. This vulnerability is actively exploited in ransomware campaigns since October 2021. Affected versions range from 19 to 22.0.9.1. It is critical to update to version 22.0.9.1 or later to mitigate the risk.

    The vulnerability is being actively exploited; treat it as a priority. CISA lists it as used in ransomware campaigns. Update BQE BillQuick Web Suite to version 22.0.9.1. Immediate actions, mitigation and detection rules are in the runbook below.

    Affected
    • BQE BillQuick Web Suite lt 19..22.0.9.1
    Fixed in
    • BQE BillQuick Web Suite 22.0.9.1

    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

    74.3 %

    EPSS score

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

    Source: FIRST EPSS, percentile 99.49

    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
    253.17 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.

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    actively exploited
    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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    74.3 %
    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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    99.49
    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

    Response and mitigation

    Why act now?

    Prioritisation rationale

    This flaw can be exploited over the network with no authentication and no user interaction, and it leads straight to OS command execution on the database server via xp_cmdshell. CISA flags it as used in ransomware campaigns, and its exploitation likelihood ranks among the very highest of all CVEs. BillQuick is typically used by architecture, engineering, accounting and consulting firms for time tracking and billing. These deployments are often published directly to the internet and hold sensitive client and financial data. Treat any internet-reachable unpatched instance as a top-priority emergency and investigate it as potentially already compromised. Patch internal-only instances within days, since they give an attacker who already has a foothold an easy path for lateral movement.

    1. Runbook step 1

      Immediate response (0-24 h)

      • Find and cut exposure: Identify every internet-facing BillQuick Web Suite instance (IIS, typically TCP 80/443). Until it is patched, restrict access to VPN or internal ranges via a firewall rule or IIS IP restrictions.
      • Patch: Upgrade BillQuick Web Suite to 22.0.9.1 or later. Versions 2018 through 2021 before 22.0.9.1 are affected. Check BQE's vendor advisory for the currently recommended build and go straight to the latest release where possible.
      • Kill xp_cmdshell: On the backing MSSQL instance, run EXEC sp_configure 'xp_cmdshell',0; RECONFIGURE;. Then check whether the option was enabled at any point since October 2021, because that is the path to code execution as MSSQLSERVER$.
      • Compromise assessment: Hunt on the web and SQL hosts for child processes of sqlservr.exe, new services and scheduled tasks, and unfamiliar binaries in temp directories. Isolate on any hit and invoke the ransomware IR plan.
      • Rotate credentials: If compromise is suspected, rotate sa, the connection-string credentials in web.config, local admin accounts on the SQL host, and BillQuick user passwords. The database holds billing and client data, so assess GDPR/NIS2 reporting obligations.
      • Protect backups: Verify offline or immutable copies of the BillQuick database and file shares before starting any cleanup.

    2. Runbook step 2

      Mitigation layers

      • Network segmentation: Publish BillQuick only behind VPN or an authenticating reverse proxy (e.g. Entra ID App Proxy or an SSO gateway). Allow SQL (TCP 1433) from the web server only. Apply default-deny egress from the SQL host to the internet to break payload staging via certutil, bitsadmin or PowerShell.
      • WAF/IPS: Add a rule on POST requests to the login page that inspects the txtID parameter. Block SQL metacharacters and keywords (', --, ;, xp_cmdshell, EXEC, CONVERT(, WAITFOR DELAY, UNION SELECT), and run the OWASP CRS SQLi rules (942xxx) in blocking mode.
      • Database hardening: The application login should not be sysadmin and should not hold rights to sp_configure. Keep xp_cmdshell permanently disabled and run the SQL service under a virtual or gMSA account without local admin rights.
      • Endpoint hardening: Use ASR rules, AppLocker or WDAC to stop sqlservr.exe from spawning cmd.exe, powershell.exe, rundll32.exe, mshta.exe or certutil.exe. Run EDR in block mode on both hosts.
      • IIS configuration: Disable verbose ASP.NET errors (customErrors mode="On"), since leaked error messages make the injection easier. Make sure IIS logging captures all relevant fields, and capture request bodies via the WAF where IIS cannot.

    3. Runbook step 3

      Detection rules

      • EDR/Sysmon EID 1 or Security EID 4688: Look for a parent process of sqlservr.exe spawning a shell or LOLBin. KQL: DeviceProcessEvents | where InitiatingProcessFileName =~ "sqlservr.exe" and FileName in~ ("cmd.exe","powershell.exe","certutil.exe","bitsadmin.exe")
      • MSSQL / Windows Application log: Event ID 15457 with "Configuration option 'xp_cmdshell' changed from 0 to 1", and Event ID 15281 (attempt to use a disabled component). Treat any change outside a change window as critical.
      • IIS access logs/WAF: Bursts of POSTs to the BillQuick login page returning HTTP 500 from a single source, or txtID values containing SQL syntax. SPL: index=iis cs_uri_stem="*default.aspx*" sc_status=500 | stats count by c_ip | where count>10
      • Network telemetry (Zeek/Suricata): Outbound HTTP, SMB or DNS connections from the SQL or web server to unfamiliar external destinations, especially executable downloads (files.log with mime_type = application/x-dosexec).
      • Ransomware precursors: Sysmon EID 11 for new .exe or .ps1 files in C:\Windows\Temp or C:\ProgramData written by the SQL service account. Also watch for vssadmin delete shadows or wbadmin delete catalog (EID 4688) and new service installs (System EID 7045).

    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

    BQE BillQuick Web Suite 2018 through 2021 before 22.0.9.1 allows SQL injection for unauthenticated remote code execution, as exploited in the wild in October 2021 for ransomware installation. SQL injection can, for example, use the txtID (aka username) parameter. Successful exploitation can include the ability to execute arbitrary code as MSSQLSERVER$ via xp_cmdshell.

    Source: NVD (NIST), cvelistv5, CISA KEV Catalog, 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
    bqebillquick_web_suite
    • 19 – < 22.0.9.1
    • 22.0.9.1

    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

    • huntress.comblog/threat-advisory-hackers-are-exploiting-a-vulnerability-in-…x_refsource_MISC, Exploit, Third-party advisory
    • cisa.govknown-exploited-vulnerabilities-catalog?field_cve=CVE-2021-42258government-resource, US government resource
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