Did KB5063878 Cause SSD Failures in Windows 11 24H2—or Was It a Silent Fix?

BornCity’s latest dispatch raises a subtle but important question: did Microsoft quietly neutralize the wave of SSD failures reported from Japan after the August 2025 Windows 11 24H2 roll‑out, or did the alarm simply fade after vendors and Redmond concluded they could not reproduce a systemic fault? (borncity.com) (borncity.com)

Background​

The issue began as a concentrated set of user reports from Japan in mid‑August 2025 alleging that the Windows 11 24H2 cumulative security update (KB5063878, published August 12, 2025) could cause SSDs and, in some cases, HDDs to disappear or become inaccessible during large sustained writes. A commonly reported pattern: drives more than ~60% full, subject to tens of gigabytes of continuous writes (roughly 50 GB in community tests), would suddenly vanish from Device Manager and the OS; in some instances SMART telemetry appeared to stop and files became unreadable. Early community testing flagged Phison‑controller and other DRAM‑less designs as disproportionately affected. (borncity.com) (tomshardware.com)
Major technology outlets and community forums amplified the story as users published workload reproductions and partial recovery write‑ups. Independent reporting captured the alarm and the vendor responses that followed. (tomshardware.com, windowscentral.com)

What the BornCity posts say​

• BornCity first documented the Japanese user reports and conservative community warnings — advising administrators to delay KB5063878 deployments until the matter was understood. The blog reproduced the test symptoms and the suspected link to Phison controllers and DRAM‑less SSDs. (borncity.com)
• Subsequent BornCity updates tracked Microsoft’s investigation and the vendor coordination that followed. By early September BornCity reported that Microsoft’s inquiry — including joint testing with hardware partners — had not found evidence that the August cumulative caused a systemic wave of SSD failures. That update essentially described the problem as unresolved socially (lots of reports) but unproven technically: Microsoft said it could not reproduce the failures with current telemetry and internal testing. BornCity’s coverage framed this as an apparent “all‑clear” from Microsoft while noting lingering anecdotal reports. (borncity.com)
• On September 6 BornCity asked whether a silent fix had been rolled out that addressed the Japanese reports — an observation consistent with the decrease in fresh public reports and the vendor statements — but BornCity flagged the lack of clear, explicit change logs or advisory explaining such a silent corrective action. This is the kernel of the “silent fix” claim: fewer new incidents, vendors reporting no reproducible fault, and Microsoft’s investigation concluding there was no link. That combination can look, in practice, like a fix applied beneath public view — or like a problem that proved to be isolated or misattributed. (borncity.com)

Timeline recap (concise)​

• August 12, 2025 — Microsoft ships the August cumulative for Windows 11 24H2 (KB5063878). (windowscentral.com)
• Mid‑August 2025 — Japanese user(s) publish reproducible tests showing SSD disappearance under large writes; community testers report similar results in many consumer‑grade drives. (borncity.com, tomshardware.com)
• Vendors and Microsoft begin investigating; Phison and Microsoft run extended tests. (bleepingcomputer.com, techradar.com)
• Late August — Microsoft posts service alerts and collects reports; third‑party labs and vendors perform multi‑thousand‑hour test runs. (bleepingcomputer.com, techradar.com)
• Early September — Microsoft concludes it cannot reproduce a systemic link between KB5063878 and the reported drive failures; public incident reports slow down. BornCity and other outlets cover the development and ask whether a “silent fix” explains the change in signal. (borncity.com, windowscentral.com)

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The technical picture: why SSDs can be brittle around OS changes​

At a systems level, modern SSDs are tightly co‑designed with their firmware and controllers. Two technical concepts are central to this episode:

• Host Memory Buffer (HMB): some DRAM‑less NVMe SSDs borrow a slice of host RAM to store mapping tables and caches. HMB allocation policies are implemented by the OS driver and the SSD controller/firmware, and mismatches in expected HMB size or timing can stall the drive or trigger recovery paths in firmware. A previous 24H2‑era episode (WD/SanDisk) involved HMB allocation differences that caused BSODs until vendors released firmware updates. That earlier history informed cautious responses when new storage problems surfaced. (answers.microsoft.com, borncity.com)
• Controller/firmware edge cases: controller logic (Phison, InnoGrit, Maxio, etc.) implements wear leveling, cache flushing, and internal mapping. Large sequential writes under specific fullness conditions (e.g., >60% occupied) stress these mechanisms differently than typical desktop use. If firmware hits an untested corner case, a drive may stop responding until a reset or deeper tool intervention. Community testers reported that the failure mode sometimes left drives temporarily or permanently inaccessible without vendor tools. (tomshardware.com, amagicsoft.com)

These interactions are inherently complex: an OS update that subtly changes I/O timing, caching hints, or driver behavior can expose latent firmware bugs — or reveal already‑failing batches of hardware. That makes root‑cause analysis hard: reproducibility depends on controller firmware, SSD fullness, the precise write pattern, and the host’s driver stack.

What vendors and Microsoft reported​

• Microsoft: after conducting internal testing and collaborating with storage partners, Microsoft said it found no link between KB5063878 and the reported failures; it was unable to reproduce the problem in its labs and reported no telemetry spike of drive failures across its installed base. Microsoft continued to collect data from affected users for further analysis. (bleepingcomputer.com, windowscentral.com)
• Phison and other controller vendors: Phison publicly ran multi‑thousand‑hour test cycles and did not reproduce the failures in their validation runs; they likewise reported no spike in partner RMAs that would indicate a large‑scale hardware failure. Phison’s work and Microsoft’s joint testing were central to the public conclusion that a systemic OS‑triggered failure was not evident. (techradar.com, bleepingcomputer.com)
• Independent media and test labs: Tom’s Hardware and other outlets documented community reproduction tests that did show vanishing drives under certain workloads in lab conditions. Those tests contributed to the alarm and were used by vendors to narrow investigation parameters. Independent reporting emphasized that the problem appeared concentrated in narrowly defined conditions and may not reflect mass‑market failure telemetry. (tomshardware.com, windowscentral.com)

Taken together, the vendor and Microsoft statements form a credible counterpoint to the worst readings of the initial reports: tests in controlled industrial environments failed to reproduce a broad systemic defect; telemetry across millions of devices did not show large failure spikes. But those facts do not automatically disprove every anecdotal failure — particularly for edge conditions and small hardware batches.

The “silent fix” hypothesis: what it means and whether it holds up​

BornCity’s suggestion that a “silent fix” might explain the falloff in reports is shorthand for three possible, non‑exclusive scenarios:

• Microsoft or an OEM quietly released an invisible mitigation (driver tweak, back‑end telemetry rule, or release‑health flag) that reduced exposure.
• Vendors issued firmware or update mechanisms that fixed affected drives — but those actions were incremental and not widely publicized as an explicit response to KB5063878.
• The initial cluster of reports reflected an isolated hardware batch, misconfiguration, or workload artifact that naturally subsided — and so fewer new incidents were reported.

Which of these is most likely?

• Evidence that Microsoft and Phison ran extended tests and reported no reproducible fault argues against a major OS patch being rolled out specifically to solve the problem. Microsoft’s service alert and vendor test summaries were explicit that they did not observe a systemic correlation. That weakens the “Microsoft quietly fixed it” interpretation. (bleepingcomputer.com, techradar.com)
• On the other hand, vendors frequently push firmware updates and drive‑management tools quietly or as routine maintenance, and many users apply such updates automatically (e.g., via vendor dashboards). Firmware fixes that address controller edge cases often go unheralded outside vendor advisories. If a small number of drives were affected and vendor firmware was effective, that could look like a silent remediation. Tom’s Hardware and independent threads showing mixed device recoveries lend credence to firmware being a plausible mitigation vector. (tomshardware.com, borncity.com)
• BornCity’s phrasing is careful — it asks whether a silent fix occurred rather than asserting it as fact. That restraint is appropriate because the public record shows either a) no systemic OS fix was announced or b) vendors and Microsoft closed the investigation without a public remediation bulletin. In short: a silent, incremental vendor‑side fix is possible, but Microsoft’s public position is that KB5063878 was not the root cause, which undercuts a claim that Redmond quietly rolled out a corrective patch for the problem it caused. (borncity.com, bleepingcomputer.com)

Short‑term guidance for users and administrators​

Given uncertainty, conservative risk management is smart. Practical steps that will reduce exposure and preserve data:

• Backup first: ensure current full backups or system images before installing cumulative updates or running large data transfers. Backups are the last line of defense against unrecoverable device failures. (windowscentral.com)
• Delay non‑critical updates in production: hold KB5063878 and similar optional updates in managed WSUS/Intune rings for at least one test cycle if you operate large fleets that run heavy write workloads. BornCity and other outlets recommended caution while investigations were ongoing. (borncity.com)
• Avoid very large sequential writes on suspicious drives: community tests indicated the problem was most reproducible with large (>50 GB) writes to drives that were heavily used (>60% full). Where possible, schedule large data migrations to drives known to be healthy, or stage writes in smaller chunks. (tomshardware.com)
• Update SSD firmware and vendor tools: check for vendor firmware releases and vendor management tools (e.g., WD Dashboard, SanDisk utilities, vendor firmware utilities) and apply them in a controlled pilot. Earlier HMB‑related BSODs were remedied by firmware fixes combined with Microsoft safeguards. (borncity.com, answers.microsoft.com)
• Monitor telemetry and error indicators: watch for Event Viewer messages and SMART errors. If drives disappear, stop writing to them — imaging the device (dd, vendor tools) before further writes preserves chances of recovery. (windowsforum.com)
• Use vendor support when needed: drives that remain inaccessible after reboot often require vendor low‑level tools or RMA; don’t assume OS reinstall will fix a hardware failure. (tomshardware.com)

Why the community response matters (and what it reveals)​

This episode illustrates several realities of modern PC ecosystems:

• Edge cases can create loud signals. A small set of reproducible failures in tightly constrained conditions can generate outsized social attention on social platforms, especially when data loss is involved.
• Industrial testing has limits. Vendors and Microsoft can run thousands of hours of tests but still miss a rare hardware batch, environmental condition, or user workload that triggered an edge failure for a few users.
• Communication matters. When community reporters and vendors disagree in tone — users claiming reproducible failures vs vendors saying they cannot reproduce anything systemic — trust frays. Transparent, timely advisories (even “under investigation” posts) reduce speculation.
• Patch management is complex. The tradeoff between quick fixes and broader platform stability is real; applying rapid changes risks new regressions, while dragging the process out prolongs uncertainty for users with sensitive workloads.

Critical analysis — strengths and risks of how this incident played out​

Strengths

• Rapid community detection. The early publication of test cases by Japanese users and independent labs accelerated investigation and focused vendor attention. That’s a functioning community safety net. (tomshardware.com)
• Vendor and Microsoft coordination. Public statements show collaboration and large‑scale testing; Phison’s extensive test cycles and Microsoft’s telemetry review are proper industrial responses to a serious allegation. (bleepingcomputer.com, techradar.com)
• Practical mitigations were available. Firmware updates, registry workarounds (to limit HMB allocation), and Microsoft’s safeguard blocks for earlier HMB/WD incidents provided pragmatic options for admins to protect fleets. (answers.microsoft.com)

Risks and weaknesses

• Ambiguity in public messaging. Saying “we cannot reproduce” while users report real losses leaves victims without satisfying explanations. It also fuels conspiracy theories about “silent fixes” when the public record shows only quiet back‑channel activity (firmware updates, telemetry changes). (bleepingcomputer.com, borncity.com)
• Incomplete root‑cause closure. Even when telemetry lacks a widespread failure signal, single‑case data loss events carry high impact. Without a detailed public root‑cause postmortem (drive serial ranges, firmware versions, exact OS kernel behaviors), administrators are left making risk decisions in the dark.
• Potential for uneven firmware coverage. Not all users keep firmware tools updated, and not all vendors push fixes through Windows Update. If remediation relies on vendor firmware uptake, some devices may remain vulnerable longer than announced. (borncity.com)

Recommended monitoring checklist for Windows 11 24H2 admins​

• Verify backup and disaster‑recovery plans are current for all endpoints.
• Create a pilot ring: apply KB5063878 to a representative test group, run stress workloads (large sequential writes) against common SSD models.
• Record firmware versions and controller families for each test device. If issues emerge, document exact write patterns and fullness thresholds.
• Subscribe to vendor security advisories for Phison, WD, SanDisk, Kioxia, Corsair, and the Windows release‑health dashboard.
• Keep an eye on community test writeups (Tom’s Hardware reproducibility tests, BornCity updates) while prioritizing vendor advisories and telemetry. (tomshardware.com, borncity.com)

Conclusion​

The raw facts: a small but alarming cluster of SSD disappearance and corruption reports from Japan triggered intense scrutiny after Microsoft’s August 2025 cumulative (KB5063878). Community tests reproduced failures under narrow write patterns; vendors and Microsoft ran extensive tests and declared they could not reproduce a systemic bug tied to the update. That left outlets such as BornCity to wonder whether an official or vendor “silent fix” had been applied — or whether the issue had been a narrow, non‑reproducible anomaly that naturally subsided. (borncity.com, bleepingcomputer.com)
For administrators and power users the practical takeaway is unchanged: treat drive failures as a serious, data‑loss risk — maintain current backups, test updates in controlled rings, update SSD firmware proactively, and avoid long, heavy writes on drives that are heavily utilized until you have validated both firmware and OS behavior in your environment. The public record now leans toward no systemic OS‑wide fault discovered by vendors and Microsoft, but that verdict does not erase the real losses reported by some users — and so cautious, evidence‑driven operations remain the best defense. (techradar.com, bleepingcomputer.com)

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Appendix — Quick reference links and items to watch (for administrators)

• Look for vendor firmware advisories for Phison, WD, SanDisk, Kioxia, Corsair.
• Monitor Microsoft’s Windows release‑health pages and the Windows Update history for any out‑of‑band or reissued KBs.
• If you’re an affected user: stop writing to the drive, image it if possible, and contact the SSD vendor for recovery guidance or RMA options. (tomshardware.com, bleepingcomputer.com)

Caution: some claims in early community posts remain anecdotal and — while alarming — were not confirmed by vendor telemetry or replicated in industrial test labs. Treat unverified single‑user reproductions as important signals to investigate, but not definitive proof of a universal regression. (borncity.com, bleepingcomputer.com)

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Source: BornCity Windows 11 24H2: Silent fix for (Japanese) SSD problems? | Born's Tech and Windows World