Microsoft’s January baseline cumulative, KB5074109, delivers a heavy set of security and quality fixes — including an important NPU power-state correction and preparatory Secure Boot certificate work — but it also introduced a client-side regression that can break Azure Virtual Desktop (AVD) and Windows 365 Cloud PC connections in some managed environments; Microsoft has acknowledged the issue and published a Known Issue Rollback (KIR) mitigation while an out‑of‑band fix is prepared.
Background / Overview
KB5074109 is the January 13, 2026 cumulative baseline for Windows 11 (applies to versions 24H2 and 25H2). The package is delivered as a combined Servicing Stack Update (SSU) plus Latest Cumulative Update (LCU), which affects installation sequencing and rollback behavior for offline image teams and managed fleets. After installation systems should show OS builds
26100.7623 (24H2) or
26200.7623 (25H2). This release is primarily a security baseline: industry trackers and vendor summaries put the January security footprint at roughly
112–114 CVEs, including at least one issue observed exploited in the wild involving Desktop Window Manager. The exact CVE counting method can vary by tracker, so treat the 112–114 figure as a close estimate rather than an immutable total. Beyond the security rollup, KB5074109 bundles several targeted quality changes that matter operationally:
- A fix for an NPU (Neural Processing Unit) idle-state bug that could leave some NPUs powered while the device was idle, increasing battery drain on NPU-equipped laptops.
- Preparatory mechanics to support a phased rollout of replacement Secure Boot certificates ahead of an expiration window in mid‑2026.
- Removal of several legacy in‑box modem drivers.
- Networking and WSL fixes, and an update to WinSqlite3.dll to reduce false-positives from some security products.
These improvements explain why administrators will want to install KB5074109 on many systems — the security surface reduction and NPU battery correction are meaningful — but the package’s low-level touches also increase the chance of unpredictable interactions on complex fleets.
What’s in KB5074109 (technical snapshot)
Builds, packaging and rollback implications
KB5074109 is published as a combined SSU + LCU. That packaging reduces installation failures for most update paths but makes part of the servicing stack effectively persistent after install; removing the LCU is possible but the SSU cannot be removed without an image restore. For offline servicing and golden images, follow DISM sequencing guidance and validate your image pipeline.
Security: breadth and urgency
Independent security trackers and vendor advisories treat January’s baseline as a substantial patch set covering over a hundred CVEs, with a small number rated
Critical and several
Important. At least one DWM-related information‑disclosure bug has been observed in the wild; that alone is a strong reason to prioritize patching high‑risk endpoints. Use your normal exposure‑based prioritization (internet‑facing, privileged endpoints first).
NPU power-state fix
Devices with on‑board NPUs (used for on‑device AI acceleration) could see measurable battery improvements after installing KB5074109 and rebooting. The update corrects power transitions so eligible NPUs enter low‑power states when idle. This is a clear, verifiable quality improvement for AI-capable laptops and handhelds.
Secure Boot certificate preparation
KB5074109 adds device‑targeting metadata so Microsoft can phase the distribution of replacement Secure Boot certificates to eligible devices only after telemetry confirms successful updates. This is a conservative, telemetry‑driven rollout intended to reduce boot-risk when certificates are updated later in 2026. Test firmware/UEFI interactions on representative hardware before broad deployment.
The AVD / Cloud PC regression: symptoms, scope and immediate impact
What administrators and users saw
Within hours of the January 13 rollout, multiple administrators and community operators reported that launching an AVD or Windows 365 Cloud PC session using the
Windows App client failed immediately with an authentication error. A commonly observed dialog read:
“An authentication error has occurred (Code: 0x80080005).”
Error code: 0x0 (extended error: 0x0)
Affected endpoints could not complete a session establishment from the Windows App; the failure generally occurred before a backend authentication exchange could complete. Reproductions on multiple tenants and client configurations confirmed this behavior in many environments.
Why this is high‑impact
AVD and Windows 365 Cloud PCs are mission‑critical for many remote‑work and VDI deployments. A client‑side credential prompt regression prevents session negotiation before the cloud gateway is ever engaged, producing a synchronous outage across any device that has the problematic client behavior after the update. That makes this regression operationally urgent for affected enterprises.
Microsoft’s initial response
Microsoft promptly documented the symptom in the KB’s Known Issues section and published
KIR (Known Issue Rollback) artifacts intended for managed environments. The vendor recommended two pragmatic mitigations while engineering prepares a permanent servicing fix:
- Deploy the KIR package (MSI/Group Policy) to surgically reverse the problematic client change without uninstalling the full LCU.
- Use alternative connection paths: the AVD web client (browser-based) or the classic Remote Desktop (MSRDC) client as temporary workarounds.
Community reproductions showed that uninstalling the LCU restored AVD connectivity in many cases; however, uninstalling a baseline LCU removes significant security fixes and should be considered a last resort compared with KIR.
Root cause status and evidence
At the time of publication, Microsoft’s public guidance frames the issue functionally (credential prompt/authentication failure) and focuses on mitigation rather than a line‑by‑line engineering root cause. Community diagnostics and the symptom profile strongly point to a regression in the
credential prompt or token exchange path on the Windows client when using the Windows App to connect to AVD/Cloud PCs; this is consistent with the immediate failure behavior observed in the field. Until Microsoft publishes an engineering post‑mortem, any claim about the exact function or module remains unverified.
Gaming and display reports: what’s verified and what’s anecdote
Shortly after KB5074109 began rolling out, community threads reported a variety of display-related anomalies on a subset of systems: black screens, temporary GPU hangs, and frame-rate drops in certain titles and configurations. These reports are heterogeneous: many users saw no change, while others reported severe degradation. Independent editorial experience with previous updates shows this pattern can occur when low-level servicing interacts with GPU driver timing — sometimes the correct fix is a GPU driver update from the vendor rather than an OS rollback.
Notable points to keep in mind:
- There is no vendor-wide bulletin from NVIDIA or AMD at the time of writing that universally blames KB5074109 for a measurable FPS collapse across all systems. When vendor-level guidance is needed, manufacturers typically issue targeted hotfix drivers.
- Community claims of specific frame‑rate drops (for example, “exactly 20 FPS lost on NVIDIA 40-series in Game X”) are inherently variable and depend on GPU driver version, game engine, resolution, in-game settings, overlays, and even background tasks. Treat those numbers as anecdotal until reproducible lab tests are published.
Practical advice for gamers and high‑performance users: install the latest vendor GPU drivers before applying the OS update, pilot the update on a representative machine, and if you see regressions, test driver rollback or vendor-provided hotfixes in this order:
- Install the most recent stable driver from NVIDIA/AMD.
- If problems persist, try the previously stable driver (rollback).
- If still unresolved, pause KB5074109 on your primary gaming rig until a consensus fix appears.
Practical mitigation and deployment playbook (enterprise)
The immediate goal for IT is to restore availability while preserving as much security posture as possible. The following sequence is the pragmatic playbook many organizations adopted after the KB5074109 rollout:
- Inventory & scope
- Identify endpoints using AVD/Windows 365 and verify which devices have KB5074109 installed (use winver.exe or DISM):
DISM /online /get-packages | findstr 5074109.
- Pause deployment
- Halt further ring progression until a pilot validation completes; avoid pushing KB5074109 to broad production rings if AVD dependency exists.
- Preferred mitigation: KIR
- Deploy Microsoft’s KIR MSI/Group Policy package targeted to affected OUs or Intune device groups; a restart is required to activate the rollback. KIR is the safest operational approach because it preserves the remainder of the security and quality fixes while reversing only the offending change.
- Temporary user workarounds
- Guide users to the AVD web client or the classic Remote Desktop client until the client-side issue is fixed.
- Last resort: LCU uninstall
- If KIR isn’t feasible and business continuity demands it, you can remove the LCU with DISM and block reinstallation — but understand this reopens the security exposure the LCU addressed and complicates remediation. Use this path only after careful risk assessment. Example removal pattern (after enumerating the package name):
dism /online /remove-package /packagenameACKAGE_ID.
- Monitoring & communication
- Track Microsoft’s release health dashboard and vendor driver advisories; communicate clearly with users about fallbacks and expected timelines.
The intent behind KIR is precisely to avoid the binary choice between security and availability; use it where your management tooling and change windows allow.
Risk analysis: strengths, weaknesses and operational tradeoffs
Strengths (what Microsoft did well)
- Rapid acknowledgment and mitigation: Microsoft added the regression to the KB Known Issues and provided a KIR artifact quickly — a mature operational pattern that reduces the need for wide uninstall campaigns.
- Security-first baseline: The package patches a large collection of CVEs (roughly 112–114), including at least one actively exploited issue; delaying this baseline across all endpoints carries real risk.
- Targeted NPU and Secure Boot work: The NPU power fix is tangible for AI-enabled mobile devices, and the phased Secure Boot certificate mechanism is a conservative approach to a potentially disruptive firmware change.
Weaknesses and risks
- Client‑side regressions with outsized impact: Changes affecting authentication/credential prompts can immediately block cloud‑hosted desktop access at scale — a fragile intersection of client code and cloud authentication flows.
- SSU persistence complicates rollback: The combined SSU+LCU packaging means offline and image rollback paths are more complex; uninstalling the LCU does not remove the SSU, so golden‑image management must adapt.
- Heterogeneous hardware interactions: Low‑level servicing touches many subsystems; interactions with GPU drivers or OEM firmware may surface only in the wild, requiring vendor cooperation for targeted fixes.
Clear recommendations (by audience)
For enterprise administrators and IT teams
- Pause broad rollouts if you rely on AVD or Windows 365 Cloud PCs. Inventory affected endpoints and prepare KIR distribution packages.
- If you must maintain availability immediately, deploy KIR rather than uninstalling the whole LCU. Use uninstall only as a last resort and with compensating security controls.
- Include AVD/Cloud PC login flows in your update validation suite going forward — authentication and remote‑access must be first‑class test cases for any baseline.
For gamers and high‑performance users
- Update GPU drivers before installing KB5074109 and pilot the update on a secondary rig if possible. If you see issues, roll back the driver or wait for a vendor hotfix. Do not assume a universal FPS loss; collect reproducible test data for your specific titles and settings.
For home users (no AVD dependency)
- For most consumer devices, the security fixes and NPU battery correction are worth installing after making a current backup. Microsoft notes Home/Pro devices are very unlikely to be affected by the AVD regression, but that is not an absolute guarantee — test if in doubt.
Flags and unverifiable claims
- Any precise, single‑value claim about FPS loss tied to KB5074109 (for example, “KB5074109 causes a 20 FPS drop on NVIDIA cards”) is not verifiable across the installed base. Frame‑rate changes are highly dependent on GPU model, driver, in‑game settings, and system configuration; treat community numbers as anecdotal until vendor‑level reproducible tests appear.
- Microsoft’s KB documents the Known Issue and mitigation; however, the exact engineering root cause (which function or component changed) is not publicly detailed at time of writing — treat assertions about exact code paths as speculative until Microsoft publishes an engineering analysis.
Why this matters over the long term
KB5074109 is a textbook example of the tradeoffs in modern OS servicing: frequent, security‑focused baselines reduce exploitation windows but increase the surface for surprising regressions on complex fleets where client‑side code interacts with cloud services and third‑party drivers. Microsoft’s KIR capability is an operationally mature instrument to minimize downtime without throwing away security gains, but it requires disciplined management tooling and communication to execute effectively.
Enterprises should treat authentication flows and remote‑desktop clients as high‑risk validation scenarios for every new baseline. Gamers and power users should keep driver management workflows current and pilot everything that matters to them. For home users, the security and battery fixes remain the dominant reason to accept the update, provided you maintain sensible backups and keep drivers current.
Conclusion
KB5074109 is consequential: it closes a substantial group of vulnerabilities, fixes an NPU battery drainage bug, and prepares devices for an important Secure Boot certificate rotation. At the same time, a client‑side regression affecting the Windows App credential prompt can prevent Azure Virtual Desktop and Windows 365 Cloud PC sessions from establishing on some enterprise‑managed clients. Microsoft has acknowledged the regression and published
Known Issue Rollback (KIR) artifacts and workaround guidance (web client or classic Remote Desktop) while engineering prepares a permanent fix. Administrators should prioritize targeted testing, distribute KIR where needed, and avoid wholesale LCU uninstalls unless absolutely necessary. Gamers should pilot and validate drivers; consumers should install the update after backing up.
This episode underlines a broader lesson for patch management: test widely, keep rollback playbooks ready, and treat cloud‑auth flows as first‑class test cases in update validation.
Source: filmogaz.com
https://www.filmogaz.com/102618]