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Repair Windows errors before they cause bigger problemsFix Now →Fix the driver behind crashes, sound loss and screen glitchesFind Drivers →CVE-2026-91843 is a critical stack-based buffer overflow in the unauthenticated login process of self-managed Check Point Quantum Security Management Server and Log Server, including Multi-Domain variants. The fix is delivered as a LivePatch, not a standalone build, and it applies only to supported branches at the right level. If your management or log server runs R81.10 or older, no fix is listed for it, so a supported upgrade is the remediation path. This guide explains how the flaw is reached, which builds are affected, how to apply and verify the fix, and what to do while patching is pending.
How the attack path works
The flaw sits in the login process of the management server, and that process accepts requests before any authentication takes place. Censys describes the trigger as a crafted login request containing an excessively long username. Because the username overruns a fixed-size buffer on the stack, the overflow can, according to Censys, allow remote arbitrary code execution as root. Censys published its advisory on September 16, 2026, and reports a CVSS v3.1 base score of 9.8 (critical), assigned by Check Point.
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Two points matter for triage. First, the attacker does not need a valid account, so credential hygiene does not reduce this exposure. Second, the risk follows reachability: a management or log server whose login service can be reached from networks you do not trust is the highest-priority system to fix. The public materials reviewed do not identify the exact vulnerable function or memory layout, and no reproducible exploit chain has been published. This article therefore covers detection, patching and containment, not exploitation.
Which deployments are affected
The advisories cover self-managed Quantum Security Management Server and Log Server deployments, including Multi-Domain variants. Smart-1 Cloud is reported not affected. Affected status depends on two things: the installed release, and the installed Jumbo Hotfix Take. The thresholds in the table below are Jumbo Hotfix Take numbers. They are not LivePatch Take numbers, and the two must not be compared with each other.
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| Release | Affected level reported | Remediation or status |
|---|---|---|
| R82.20 | All versions (Censys reports that no Jumbo Hotfix Take provided protection) | Install LivePatch Take 29 |
| R82.10 | Jumbo Hotfix Take 44 or lower | Install LivePatch Take 28 |
| R82 | Jumbo Hotfix Take 126 or lower | Install LivePatch Take 28 |
| R81.20 | Jumbo Hotfix Take 166 or lower | Install LivePatch Take 28 |
| R81.10 | Jumbo Hotfix Take 190 or lower | End of support; no fix listed in the advisories. Upgrade to a supported branch. |
| R81, R80.40, R80.30, R80.20, R80.10, R80 | All versions | End of support; no fix listed in the advisories. Upgrade to a supported branch. |
Record the release and Jumbo Hotfix Take on every management and log server, including each Multi-Domain server, before you decide on a fix. A system at or below a listed threshold is affected, and a system at or above the fixed LivePatch Take for its branch is covered. Anything between those points needs the LivePatch applied.
Patching and verifying the fix
Check Point distributes the fix through LivePatch. Automatic-update enrollment may deliver it, but do not assume it arrived. Verify it on each server.
- Confirm the release and Jumbo Hotfix Take on the server, using the method in Check Point’s documentation for your release.
- Apply the LivePatch Take for your branch from the table above (R82.20 Take 29, R82.10 Take 28, R82 Take 28, or R81.20 Take 28), or let automatic update deliver it and then confirm.
- Log in to the server’s command line and run
cplp list. - Look for a LivePatch entry whose patch comment reads
CVE-2026-91843. That comment is the evidence that the fix is installed. - Repeat the check on every Multi-Domain management server and every log server. Do not treat a patch on the primary as coverage for the others.
CERT.LV, which published its advisory on September 18, 2026, uses the same cplp list check and lists fixed Takes that match the four supported branches above.
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Unsupported branches
R81.10, R81 and R80.x are end of support, and the advisories list no fix for them. Patching is not a remediation for these systems. Plan a migration to a supported branch, and treat the systems as exposed until the migration is complete. For any support exception, confirm the position directly with Check Point support rather than relying on a third-party summary.
Interim containment while patching is pending
If a LivePatch cannot be applied right away, CERT.LV recommends restricting access to the management web interface to trusted clients using Check Point Trusted Clients. This reduces exposure while you schedule the fix. It does not replace the vendor patch, and it does not remove the vulnerable login path from the software.
- Open SmartConsole or the management web interface with an administrator account.
- Go to Manage & Settings > Permissions & Administrators > Trusted Clients.
- Define the networks or hosts that need administrative access and make them the trusted clients.
- Confirm from an address outside the trusted list that the management web interface no longer responds.
- Keep the restriction in place until the LivePatch is verified with
cplp list.
Exploitation status and what the exposure count means
Censys reported, at the time of its advisory, that it had seen no public proof-of-concept and no confirmed exploitation, and that the CVE was not listed in CISA’s Known Exploited Vulnerabilities catalog. These are dated observations. They are not an assurance that systems are safe, and they can change after the date of the advisory.
Censys also observed 3,836 hosts exposing Check Point’s cp_mgmt SIC identity, which marks Security Management and Log Servers (Censys, 2026); that count shows the server roles are present on those hosts, not that they run a vulnerable build, because passive scan data did not reveal the software build or Jumbo Hotfix level.
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Repair common Windows errors and clear accumulated junk for a smoother, more stable PC - no reinstall needed.Free scan · no reinstallWhere to read the primary advisories
- Censys advisory, September 16, 2026, for the attack description, CVSS score and the release table.
- CERT.LV advisory, September 18, 2026, for the LivePatch check and the Trusted Clients mitigation. The advisory is published in Latvian.
Use the advisory pages for the latest status, since the dates above are when each source was published.
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