Linux: Use After Free
CVE-2025-71089 is a high-severity use after free vulnerability in Linux, with a CVSS 3.1 base score of 7.8 out of 10. It can be exploited with local access to the system by an attacker with a low-privileged account, without any action from a user. The record lists versions 845875f4c6788c88e2334fe5825934821decbdc8, b34289505180a83607fcfdce14b5a290d0528476, 7cad37e358970af1bb49030ff01f06a69fa7d985 as the first without the flaw, so updating Linux to one of those releases or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.16% chance of exploitation within 30 days, which is low compared with other CVEs.
High severity with no evidence of exploitation so far.
What to do
- Update Linux to 845875f4c6788c88e2334fe5825934821decbdc8 or b34289505180a83607fcfdce14b5a290d0528476 or 7cad37e358970af1bb49030ff01f06a69fa7d985 or 240cd7f2812cc25496b12063d11c823618f364e9, whichever matches your release line, or a later version.
- Update Linux Kernel to 5.15.200 or 6.1.163 or 6.6.120 or 6.12.64, whichever matches your release line, or a later version.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Linux | Linux | 26b25a2b98e45aeb40eedcedc586ad5034cbd984 up to, but not including, 845875f4c6788c88e2334fe5825934821decbdc8; 26b25a2b98e45aeb40eedcedc586ad5034cbd984 up to, but not including, b34289505180a83607fcfdce14b5a290d0528476; 26b25a2b98e45aeb40eedcedc586ad5034cbd984 up to, but not including, 7cad37e358970af1bb49030ff01f06a69fa7d985; 26b25a2b98e45aeb40eedcedc586ad5034cbd984 up to, but not including, 240cd7f2812cc25496b12063d11c823618f364e9; 26b25a2b98e45aeb40eedcedc586ad5034cbd984 up to, but not including, c2c3f1a3fd74ef16cf115f0c558616a13a8471b4; 26b25a2b98e45aeb40eedcedc586ad5034cbd984 up to, but not including, c341dee80b5df49a936182341b36395c831c2661; 26b25a2b98e45aeb40eedcedc586ad5034cbd984 up to, but not including, 72f98ef9a4be30d2a60136dd6faee376f780d06c; 5.2 | 845875f4c6788c88e2334fe5825934821decbdc8, b34289505180a83607fcfdce14b5a290d0528476, 7cad37e358970af1bb49030ff01f06a69fa7d985, 240cd7f2812cc25496b12063d11c823618f364e9, c2c3f1a3fd74ef16cf115f0c558616a13a8471b4, c341dee80b5df49a936182341b36395c831c2661 |
| Linux | Linux Kernel | 5.2 up to, but not including, 5.15.200; 5.16 up to, but not including, 6.1.163; 6.2 up to, but not including, 6.6.120; 6.7 up to, but not including, 6.12.64; 6.13 up to, but not including, 6.18.4 | 5.15.200, 6.1.163, 6.6.120, 6.12.64, 6.18.4 |
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- LocalThe attacker needs local access or must trick a user into running something.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- LowA basic user account is enough.
- User interaction
- NoneNo action by a victim is required.
- Scope
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- HighAll data handled by the component can be read.
- Integrity
- HighData or code can be modified at will.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H. Scored by NVD.
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 3.1 | 7.8 | High | CNA |
| CVSS 3.1 | 7.8 | High | NVD |
Official description
In the Linux kernel, the following vulnerability has been resolved: iommu: disable SVA when CONFIG_X86 is set Patch series "Fix stale IOTLB entries for kernel address space", v7. This proposes a fix for a security vulnerability related to IOMMU Shared Virtual Addressing (SVA). In an SVA context, an IOMMU can cache kernel page table entries. When a kernel page table page is freed and reallocated for another purpose, the IOMMU might still hold stale, incorrect entries. This can be exploited to cause a use-after-free or write-after-free condition, potentially leading to privilege escalation or data corruption. This solution introduces a deferred freeing mechanism for kernel page table pages, which provides a safe window to notify the IOMMU to invalidate its caches before the page is reused. This patch (of 8): In the IOMMU Shared Virtual Addressing (SVA) context, the IOMMU hardware shares and walks the CPU's page tables. The x86 architecture maps the kernel's virtual address space into the upper portion of every process's page table. Consequently, in an SVA context, the IOMMU hardware can walk and cache kernel page table entries. The Linux kernel currently lacks a notification mechanism for kernel page table changes, specifically when page table pages are freed and reused. The IOMMU driver is only notified of changes to user virtual address mappings. This can cause the IOMMU's internal caches to retain stale entries for kernel VA. Use-After-Free (UAF) and Write-After-Free (WAF) conditions arise when kernel page table pages are freed and later reallocated. The IOMMU could misinterpret the new data as valid page table entries. The IOMMU might then walk into attacker-controlled memory, leading to arbitrary physical memory DMA access or privilege escalation. This is also a Write-After-Free issue, as the IOMMU will potentially continue to write Accessed and Dirty bits to the freed memory while attempting to walk the stale page tables. Currently, SVA contexts are unprivileged and cannot access kernel mappings. However, the IOMMU will still walk kernel-only page tables all the way down to the leaf entries, where it realizes the mapping is for the kernel and errors out. This means the IOMMU still caches these intermediate page table entries, making the described vulnerability a real concern. Disable SVA on x86 architecture until the IOMMU can receive notification to flush the paging cache before freeing the CPU kernel page table pages.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Use After Free
The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory belongs to the code that operates on the new pointer.
How developers prevent this class of flaw
- Choose a language that provides automatic memory management.
- When freeing pointers, be sure to set them to NULL once they are freed. However, the utilization of multiple or complex data structures may lower the usefulness of this strategy.
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: total).
- Record last changed materially (score, affected products, status or references).
References
Patches and release notes
- git.kernel.org/stable/c/240cd7f2812cc25496b12063d11c823618f364e9
- git.kernel.org/stable/c/72f98ef9a4be30d2a60136dd6faee376f780d06c
- git.kernel.org/stable/c/7cad37e358970af1bb49030ff01f06a69fa7d985
- git.kernel.org/stable/c/b34289505180a83607fcfdce14b5a290d0528476
- git.kernel.org/stable/c/c2c3f1a3fd74ef16cf115f0c558616a13a8471b4
- git.kernel.org/stable/c/c341dee80b5df49a936182341b36395c831c2661
Other references
Recent Use After Free vulnerabilities
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