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Linux KernelOperating system · Linux

CVE-2025-38434

MEDIUM · 5.5 CVSS v3.1 Published 2025-07-25
Fix available
A fix is available. Upgrade to 6.12.36 / 6.15.5 or later.
See remediation →
57/100
Remediation priority · Elevated
Zero-click Patch available

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
In the Linux kernel, the following vulnerability has been resolved: Revert "riscv: Define TASK_SIZE_MAX for __access_ok()" This reverts commit ad5643cf2f69 ("riscv: Define TASK_SIZE_MAX for __access_ok()"). This commit changes TASK_SIZE_MAX to be LONG_MAX to optimize access_ok(), because the previous TASK_SIZE_MAX (default to TASK_SIZE) requires some computation. The reasoning was that all user addresses are less than LONG_MAX, and all kernel addresses are greater than LONG_MAX. Therefore access_ok() can filter kernel addresses. Addresses between TASK_SIZE and LONG_MAX are not valid user addresses, but access_ok() let them pass. That was thought to be okay, because they are not valid addresses at hardware level. Unfortunately, one case is missed: get_user_pages_fast() happily accepts addresses between TASK_SIZE and LONG_MAX. futex(), for instance, uses get_user_pages_fast(). This causes the problem reported by Robert [1]. Therefore, revert this commit. TASK_SIZE_MAX is changed to the default: TASK_SIZE. This unfortunately reduces performance, because TASK_SIZE is more expensive to compute compared to LONG_MAX. But correctness first, we can think about optimization later, if required.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis

A detailed technical summary for this CVE is being prepared.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Linux KernelOperating system
Affected:>= 6.10, < 6.12.36>= 6.13, < 6.15.5= 6.16

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Local
Complexity
Low
Privileges
Low
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 6.12.36 / 6.15.5 or later
Fixed in 6.12.366.15.5
Vendor patch git.kernel.org →
Recommended fix High confidence

6.12.36, 6.15.5, or 6.16.1+ (depending on which branch you are on)

  1. Identify the currently running Linux kernel version using 'uname -r'
  2. Determine which version branch your kernel is from (e.g., 6.10.x, 6.13.x, or 6.16.x)
  3. For kernels in the >= 6.10, < 6.12.36 range: upgrade to kernel version 6.12.36 or later
  4. For kernels in the >= 6.13, < 6.15.5 range: upgrade to kernel version 6.15.5 or later
  5. For kernels in the 6.16.x range: upgrade to kernel version 6.16.1 or later (next stable release)
  6. After upgrade, verify the fix is applied by checking the kernel version and confirming TASK_SIZE_MAX is set to TASK_SIZE (not LONG_MAX)
Caveat This is a correctness fix; reverting to TASK_SIZE may have slight performance impact compared to LONG_MAX, but ensures proper address validation in access_ok() and get_user_pages_fast()

Generated from the published advisory — verify against the referenced sources before acting.

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2025-38434 in production — separate from our analysis above.

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