CVE-2026-43286

CVE-2026-43286 is a medium-severity vulnerability in Linux Linux Kernel with a CVSS 3.x base score of 5.5. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-401.

Key facts

Description

In the Linux kernel, the following vulnerability has been resolved: mm/hugetlb: restore failed global reservations to subpool Commit a833a693a490 ("mm: hugetlb: fix incorrect fallback for subpool") fixed an underflow error for hstate->resv_huge_pages caused by incorrectly attributing globally requested pages to the subpool's reservation. Unfortunately, this fix also introduced the opposite problem, which would leave spool->used_hpages elevated if the globally requested pages could not be acquired. This is because while a subpool's reserve pages only accounts for what is requested and allocated from the subpool, its "used" counter keeps track of what is consumed in total, both from the subpool and globally. Thus, we need to adjust spool->used_hpages in the other direction, and make sure that globally requested pages are uncharged from the subpool's used counter. Each failed allocation attempt increments the used_hpages counter by how many pages were requested from the global pool. Ultimately, this renders the subpool unusable, as used_hpages approaches the max limit. The issue can be reproduced as follows: 1. Allocate 4 hugetlb pages 2. Create a hugetlb mount with max=4, min=2 3. Consume 2 pages globally 4. Request 3 pages from the subpool (2 from subpool + 1 from global) 4.1 hugepage_subpool_get_pages(spool, 3) succeeds. used_hpages += 3 4.2 hugetlb_acct_memory(h, 1) fails: no global pages left used_hpages -= 2 5. Subpool now has used_hpages = 1, despite not being able to successfully allocate any hugepages. It believes it can now only allocate 3 more hugepages, not 4. With each failed allocation attempt incrementing the used counter, the subpool eventually reaches a point where its used counter equals its max counter. At that point, any future allocations that try to allocate hugeTLB pages from the subpool will fail, despite the subpool not having any of its hugeTLB pages consumed by any user. Once this happens, there is no way to make the subpool usable again, since there is no way to decrement the used counter as no process is really consuming the hugeTLB pages. The underflow issue that the original commit fixes still remains fixed as well. Without this fix, used_hpages would keep on leaking if hugetlb_acct_memory() fails.

Frequently asked questions

What is CVE-2026-43286?
In the Linux kernel, the following vulnerability has been resolved: mm/hugetlb: restore failed global reservations to subpool Commit a833a693a490 ("mm: hugetlb: fix incorrect fallback for subpool") fixed an underflow error for hstate->resv_huge_pages caused by incorrectly attributing globally requested pages to the subpool's reservation. Unfortunately, this fix also introduced the opposite problem, which would leave spool->used_hpages elevated if the globally requested pages could not be acquired. This is because while a subpool's reserve pages only accounts for what is requested and allocated from the subpool, its "used" counter keeps track of what is consumed in total, both from the subpool and globally. Thus, we need to adjust spool->used_hpages in the other direction, and make sure that globally requested pages are uncharged from the subpool's used counter. Each failed allocation attempt increments the used_hpages counter by how many pages were requested from the global pool. Ultimately, this renders the subpool unusable, as used_hpages approaches the max limit. The issue can be reproduced as follows: 1. Allocate 4 hugetlb pages 2. Create a hugetlb mount with max=4, min=2 3. Consume 2 pages globally 4. Request 3 pages from the subpool (2 from subpool + 1 from global) 4.1 hugepage_subpool_get_pages(spool, 3) succeeds. used_hpages += 3 4.2 hugetlb_acct_memory(h, 1) fails: no global pages left used_hpages -= 2 5. Subpool now has used_hpages = 1, despite not being able to successfully allocate any hugepages. It believes it can now only allocate 3 more hugepages, not 4. With each failed allocation attempt incrementing the used counter, the subpool eventually reaches a point where its used counter equals its max counter. At that point, any future allocations that try to allocate hugeTLB pages from the subpool will fail, despite the subpool not having any of its hugeTLB pages consumed by any user. Once this happens, there is no way to make the subpool usable again, since there is no way to decrement the used counter as no process is really consuming the hugeTLB pages. The underflow issue that the original commit fixes still remains fixed as well. Without this fix, used_hpages would keep on leaking if hugetlb_acct_memory() fails.
How severe is CVE-2026-43286?
CVE-2026-43286 has a CVSS 3.x base score of 5.5, rated medium severity. It is exploitable over local access with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.
Is CVE-2026-43286 being actively exploited?
It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (2nd percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-43286?
CVE-2026-43286 primarily affects Linux Linux Kernel. In total, 9 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2026-43286?
Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
Does CVE-2026-43286 have an EU (EUVD) identifier?
Yes. CVE-2026-43286 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-28556.
When was CVE-2026-43286 published?
CVE-2026-43286 was published on 2026-05-08 and last updated on 2026-06-17.

References

Affected products (9)

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