VulnerabilityPublished 16 Sep 2026Updated 30 Oct 2026

CVE-2026-89987: Linux kernel · mm/huge_memory: transfer the pmd dirty bit to the folio on zap

Source GCVE Database

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Authoritative record:CVE-2026-89987· High

Not known to be exploited · fixed in fe6cf984939d8e12cb33a99673c8d026c5135e68 : patch Linux kernel soon.

Data as of 30 Oct 2026, 19:21 UTC

Severity

High

Rated High by Threat Radar's AI analysis · CVSS not yet scored by NVD

Thin evidence

One scorer or none

Patch: Available – fixed in fe6cf984939d8e12cb33a99673c8d026c5135e68, fd720d3906877b3d2118cd480027e4bc6648f0c5, effe3cc6d4fdd407457eb30f7b0ef094393f0d64 +5

Exploitation evidence

Disclosed: evidence found.
CVE published 16 Sep 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 30 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

ghsa-44gm-xvpq-cmx6

What to do

Upgrade to a fixed release listed under Affected software.

Affected software

Product	Affected	Fixed in
LinuxLinux	Affected ≥ b5072380eb619786990cd9eab3ade05d09ccd89e, < fe6cf984939d8e12cb33a99673c8d026c5135e68	Fixed in fe6cf984939d8e12cb33a99673c8d026c5135e68
LinuxLinux	Affected ≥ b5072380eb619786990cd9eab3ade05d09ccd89e, < fd720d3906877b3d2118cd480027e4bc6648f0c5	Fixed in fd720d3906877b3d2118cd480027e4bc6648f0c5
LinuxLinux	Affected ≥ b5072380eb619786990cd9eab3ade05d09ccd89e, < effe3cc6d4fdd407457eb30f7b0ef094393f0d64	Fixed in effe3cc6d4fdd407457eb30f7b0ef094393f0d64
LinuxLinux	Affected ≥ b5072380eb619786990cd9eab3ade05d09ccd89e, < 9435cddf1378d149d826bd7bd1448a44bf96868d	Fixed in 9435cddf1378d149d826bd7bd1448a44bf96868d
LinuxLinux	Affected ≥ b5072380eb619786990cd9eab3ade05d09ccd89e, < 79d8c89baa10612c1675972a632c65cdbe0936f6	Fixed in 79d8c89baa10612c1675972a632c65cdbe0936f6
LinuxLinux	Affected ≥ b5072380eb619786990cd9eab3ade05d09ccd89e, < 13f4910d81b62a214cdb28b47237198fa96078a2	Fixed in 13f4910d81b62a214cdb28b47237198fa96078a2

AI-suggested

A fix has been implemented in the Linux kernel to transfer the pmd dirty bit to the folio on zap, preventing the silent data loss. Users should update to a kernel version that includes this fix. No additional mitigation is required once the patch is applied.

Description

A vulnerability in the Linux kernel's memory management subsystem causes silent data loss for processes using MAP_SHARED tmpfs segments with transparent huge pages (THP) enabled and swap enabled. The issue arises because the pmd dirty bit is not transferred to the folio on unmapping, leading to data not being swapped out and lost upon reclaim. This affects scenarios where state is shared across process generations via tmpfs, such as /dev/shm caches.

Impact

Silent data loss occurs for processes that rely on MAP_SHARED tmpfs segments with transparent huge pages enabled and swap enabled. Data written to such mappings may be discarded without being swapped out during unmapping, leading to zeroed data on subsequent access. This can cause crashes or corruption in applications that share state via tmpfs across process lifetimes, such as caches in /dev/shm.

Summary

The Linux kernel vulnerability CVE-2026-89987 involves improper handling of the pmd dirty bit during unmapping of huge page folios in tmpfs. Specifically, zap_huge_pmd_folio() propagates the pmd young bit but omits the dirty bit transfer to the folio. For tmpfs, which lacks page_mkwrite() and has vma_wants_writenotify() false, a read fault on a MAP_SHARED tmpfs mapping installs a writable pmd without marking the folio dirty. Upon unmapping, the dirty bit is lost, causing the folio to appear clean and be freed without being swapped out. This leads to silent data loss when the folio is later re-mapped, as the data is replaced with zeros. The issue manifests only with shmem THP enabled and swap enabled. The flaw was reproduced on x86_64 with tmpfs and fixed by transferring the pmd dirty bit to the folio on zap.

References

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