CVE-2026-98788
futex: Fix private hash use-after-free on resize
Description
In the Linux kernel, the following vulnerability has been resolved: futex: Fix private hash use-after-free on resize poll_state_synchronize_rcu(mm->futex.phash.batches) is used by futex_ref_drop() to check that a grace period has passed since the current hash was published. This relies on batches referencing a grace period which started after the hash pointer was assigned. __futex_pivot_hash() sets mmph->batches before it replaces mmph->hash: scoped_guard(rcu) { mmph->batches = get_state_synchronize_rcu(); rcu_assign_pointer(mmph->hash, new); } The scoped_guard(rcu) doesn't stop new grace periods from starting, and if one starts between those two assignments, futex_ref_drop() can move forward while a reader still holds a pointer to the old hash. Fix things by setting mmph->batches after assigning mmph->hash. The scoped_guard(rcu) isn't needed, so let's drop that as well.
INFO
Published Date :
Oct. 18, 2026, 4:17 p.m.
Last Modified :
Oct. 18, 2026, 4:17 p.m.
Remotely Exploit :
No
Source :
416baaa9-dc9f-4396-8d5f-8c081fb06d67
Solution
- Update the Linux kernel to the latest patched version.
- Apply the provided patch for futex hash resizing.
- Review and test changes in a controlled environment.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-98788.
| URL | Resource |
|---|---|
| https://git.kernel.org/stable/c/5d5dc18b3a9ac011619b7d3af4514bf9e9b6a6af | |
| https://git.kernel.org/stable/c/f35e3b5784221654f9cdbd6222275a7fa203f6c3 |
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-98788 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-98788
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-98788 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-98788 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
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New CVE Received by 416baaa9-dc9f-4396-8d5f-8c081fb06d67
Oct. 18, 2026
Action Type Old Value New Value Added Description In the Linux kernel, the following vulnerability has been resolved: futex: Fix private hash use-after-free on resize poll_state_synchronize_rcu(mm->futex.phash.batches) is used by futex_ref_drop() to check that a grace period has passed since the current hash was published. This relies on batches referencing a grace period which started after the hash pointer was assigned. __futex_pivot_hash() sets mmph->batches before it replaces mmph->hash: scoped_guard(rcu) { mmph->batches = get_state_synchronize_rcu(); rcu_assign_pointer(mmph->hash, new); } The scoped_guard(rcu) doesn't stop new grace periods from starting, and if one starts between those two assignments, futex_ref_drop() can move forward while a reader still holds a pointer to the old hash. Fix things by setting mmph->batches after assigning mmph->hash. The scoped_guard(rcu) isn't needed, so let's drop that as well. Added Affected New affected value received. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/98xxx/CVE-2026-98788.json">CVE-2026-98788</a> Added Reference https://git.kernel.org/stable/c/5d5dc18b3a9ac011619b7d3af4514bf9e9b6a6af Added Reference https://git.kernel.org/stable/c/f35e3b5784221654f9cdbd6222275a7fa203f6c3