CVE-2026-23100 — mm/hugetlb: fix hugetlb_pmd_shared()
In the Linux kernel, the following vulnerability has been resolved: mm/hugetlb: fix hugetlb_pmd_shared() Patch series "mm/hugetlb: fixes for PMD table sharing (incl. using mmu_gather)", v3. One functional fix, one performance regression fix, and two related comment fixes. I cleaned up my prototype I recently shared [1] for the performance fix, deferring most of the cleanups I had in the prototype to a later point. While doing that I identified the other things. The goal of this patch set is to be backported to stable trees "fairly" easily. At least patch #1 and #4. Patch #1 fixes hugetlb_pmd_shared() not detecting any sharing Patch #2 + #3 are simple comment fixes that patch #4 interacts with. Patch #4 is a fix for the reported performance regression due to excessive IPI broadcasts during fork()+exit(). The last patch is all about TLB flushes, IPIs and mmu_gather. Read: complicated There are plenty of cleanups in the future to be had + one reasonable optimization on x86. But that's all out of scope for this series. Runtime tested, with a focus on fixing the performance regression using the original reproducer [2] on x86. This patch (of 4): We switched from (wrongly) using the page count to an independent shared count. Now, shared page tables have a refcount of 1 (excluding speculative references) and instead use ptdesc->pt_share_count to identify sharing. We didn't convert hugetlb_pmd_shared(), so right now, we would never detect a shared PMD table as such, because sharing/unsharing no longer touches the refcount of a PMD table. Page migration, like mbind() or migrate_pages() would allow for migrating folios mapped into such shared PMD tables, even though the folios are not exclusive. In smaps we would account them as "private" although they are "shared", and we would be wrongly setting the PM_MMAP_EXCLUSIVE in the pagemap interface. Fix it by properly using ptdesc_pmd_is_shared() in hugetlb_pmd_shared().
Who exploits it and how urgent it is
A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.
How the score was calculated
- EPSS 0.1% (30-day exploitation probability)+0
- Technical severity (medium)+3
The score orders the patch queue; it does not replace your asset context (internet exposure, criticality, compensating controls).
Triage
Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.
Remediation
Fixes and mitigations documented by the sources — linked to the original advisory.
- Documented patch — git.kernel.org (NIST National Vulnerability Database)
- Documented patch — git.kernel.org (NIST National Vulnerability Database)
- Documented patch — git.kernel.org (NIST National Vulnerability Database)
- Documented patch — git.kernel.org (NIST National Vulnerability Database)
First 24 hours
Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.
- Identify exposed assets running the affected vendor/product/version combinations (Linux Linux, Linux Linux Kernel).
- Apply the fixed version or the patch documented under Remediation.
- Search available logs for exploit probes, errors and authentication anomalies.
Affected scope
Vendor, product and versions as the sources word them.
| Vendor | Product | Versions | Status | Source |
|---|---|---|---|---|
| Linux | Linux |
version 6.13≥ 6.12.9 and < 6.12.74≥ 6.6.72 and < 6.6.127≥ 6.1.142 and < 6.1.167≥ 5.15.186 and < 5.15.203≥ 5.10.239 and < 5.10.253≥ 59d9094df3d79443937add8700b2ef1a866b1081 and < ca1a47cd3f5f4c46ca188b1c9a27af87d1ab2216≥ 59d9094df3d79443937add8700b2ef1a866b1081 and < 69c4e241ff13545d410a8b2a688c932182a858bf and 5 more≥ 2e31443a0d18ae43b9d29e02bf0563f07772193d and < 3a18b452dd5f7f1652c2e92f8ae769aa17a66c9e≥ 56b274473d6e7e7375f2d0a2b4aca11d67c6b52f and < 51dcf459845fd28f5a0d83d408a379b274ec5cc5≥ 02333ac1c35370517a19a4a131332a9690c6a5c7 and < 5b2aec77f92265a9028c5f632bdd9af5b57ec3a3≥ 8410996eb6fea116fe1483ed977aacf580eee7b4 and < bf3c2affe245cf831866ddc8f736ae6a22cdc11c≥ 94b4b41d0cdf5cfd4d4325bc0e6e9e0d0e996133 and < 8ae48255bcb17b32436be97553dca848730d365f |
Vulnerable | CVE Program (cve.org) e CISA ADP |
| Linux | Linux Kernel |
version 6.19-rc6≥ 5.10.239 and < 5.11version 6.19-rc5version 6.19-rc4version 6.19-rc3version 6.19-rc2version 6.19-rc1version 6.13-rc7 and 7 moreversion 6.13-rc6version 6.13≥ 6.13.1 and < 6.18.8≥ 6.12.9 and < 6.12.74≥ 6.6.72 and < 6.6.127≥ 6.1.142 and < 6.2≥ 5.15.186 and < 5.16 |
Vulnerable | NIST National Vulnerability Database |
Attack characteristics
The CVSS vector, decoded. It describes the attack, not your exposure to it.
Every base score collected
Sources score independently and may disagree; each row says who scored it and under which version.
| Score | Version | Severity | Expl. | Impact | Scored by |
|---|---|---|---|---|---|
| 5.5 | CVSS 3.1 | Medium | 1.8 | 3.6 | nvd@nist.gov via NIST National Vulnerability Database |
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H (score shown at the top: nvd@nist.gov) EPSS over time FIRST
Oct 13, 2026 → Oct 14, 2026 · 2 reading(s) · max 0.14%
Detection
Read off the CVSS vector and the weakness class. Starting points, not tested rules.
- Local/physical vector: focus on endpoint telemetry (EDR) from affected hosts.
Timeline
What happened to this CVE, newest first.
- 2026
- Affected products added · linux/linux
- Record published
- Fix documented
- CVSS changed · 5.5
- Source status changed · → Modified
- Record created in this database
- CVE published
Source activity
Repeated readings are counted rather than listed.
- 1× References added · Oct 15, 2026 – Oct 15, 2026
- 1× Official description updated · Oct 13, 2026 – Oct 13, 2026
References
11 on the record
- git.kernel.org/stable/c/69c4e241ff13545d410a8b2a688c932182a858bf
- git.kernel.org/stable/c/51dcf459845fd28f5a0d83d408a379b274ec5cc5
- git.kernel.org/stable/c/3a18b452dd5f7f1652c2e92f8ae769aa17a66c9e
- git.kernel.org/stable/c/ca1a47cd3f5f4c46ca188b1c9a27af87d1ab2216
- git.kernel.org/stable/c/8ae48255bcb17b32436be97553dca848730d365f
- cert-portal.siemens.com/productcert/html/ssa-082556.html
- cert-portal.siemens.com/productcert/html/ssa-457936.html
- cert-portal.siemens.com/productcert/html/ssa-019113.html
- cert-portal.siemens.com/productcert/html/ssa-784472.html
- git.kernel.org/stable/c/bf3c2affe245cf831866ddc8f736ae6a22cdc11c
- git.kernel.org/stable/c/5b2aec77f92265a9028c5f632bdd9af5b57ec3a3
Elsewhere on this site
Related CVEs (same products)
- Critical CVE-2026-99999 ipv4: validate checksum_start before completing checksum 7h
- Unknown CVE-2026-98432 ipv4: free inet_opt and ireq_opt after an RCU grace period 7h
- Unknown CVE-2026-98424 wifi: cfg80211: undo netns switch if renaming the wiphy fails 1d
- Unknown CVE-2026-98425 wifi: mac80211: don't warn when an IBSS has no channel to scan 1d
- Unknown CVE-2026-98426 wifi: mwifiex: fix IRQ leak using wrong index in MSI-X error path 1d
- Unknown CVE-2026-98427 net/sched: codel: bound the dropping loop per dequeue call 1d
Not in any source we poll
Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.
- No CISA SSVC assessment.
- No CWE classification.
- No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
- No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
- No exploit packet captures, log samples, or incident case IDs supplied.
Answered from this record
Text assembled only from the fields above — no additional claims.
What should defenders know first?
CVE-2026-23100 is "mm/hugetlb: fix hugetlb_pmd_shared()", rated Medium. It affects Linux (Linux); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. CVSS 5.5 describes technical severity. EPSS 0.14% estimates the probability of exploitation in 30 days; neither replaces your asset context. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.
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