CVE-2021-27766
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedThe BigFix Client installer is created with InstallShield, which was affected by CVE-2021-41526, a vulnerability that could allow a local user to perform a privilege escalation. This vulnerability was resolved by updating to an InstallShield version with the underlying vulnerability fixed.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · high confidenceThe BigFix Client installer is built with InstallShield, which contains CVE-2021-41526 vulnerability. This flaw allows a local unprivileged user to perform privilege escalation during or after the installation process, potentially gaining SYSTEM-level access.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.
NVD · CPE data>= 9.5, <= 9.5.18>= 10, <= 10.0.5CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Local
- Complexity
- Low
- Privileges
- Low
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- High
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Check installed BigFix Client versionOpen Windows Registry and navigate to HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall\{BFD8B610-2C88-4D2A-9D0E-2B4A3E7A562F} (or search for BigFix in Uninstall registry), or run 'bigfix.exe -version' from the BigFix client directoryAffected if Version is >= 9.5 and <= 9.5.18, or >= 10.0 and <= 10.0.5
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Identify BigFix installer files on systemSearch for installer files: look for 'BigFix Windows Client.exe', 'BESClient-*.msi', or similar installer files in common locations such as C:\Program Files\BigFix, C:\Users\*\Downloads, or shared installer repositoriesAffected if Installer files exist on the system that were created with vulnerable InstallShield versions
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Check for unauthorized SYSTEM-level processesOpen Task Manager or run 'tasklist /v' and look for processes running under the SYSTEM account that were not initiated by an administrator, or check Event Viewer Security logs for new accounts created or privilege escalation events around installation timesAffected if SYSTEM-level processes exist or privilege escalation events occurred that correlate with BigFix installation timing
A system is affected if the BigFix Client version falls within 9.5 through 9.5.18 or 10.0 through 10.0.5, or if installer files built with vulnerable InstallShield versions are present on the system.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
dbcve · scopedRebuild the BigFix Client installer using a version of InstallShield that incorporates the CVE-2021-41526 fix, then distribute the updated installer to replace vulnerable versions.
BigFix Platform 10.0.6 or later (10.x), or 9.5.19 or later (9.5.x)
- Upgrade BigFix Platform to version 10.0.6 or later for the 10.x release line
- Alternatively, upgrade to version 9.5.19 or later for the 9.5.x release line
- After upgrading, verify the BigFix Client installer uses a patched InstallShield version by reviewing release notes or contacting HCL/BigFix support
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation2.0 h
- Implementation8.0 h
- Testing4.0 h
- Review / QA2.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $4,480.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-27766 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2021-27766 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.
- Verified mitigations, workarounds, and config changes
- Version or environment caveats, and links to real fixes
- No weaponised exploit code, or anything meant to cause harm
- No spam, self-promotion, credentials, or personal data