Linux Kernel up to d1347977661342cb09a304a17701eb2d4aa21dec should_flush_tlb privilege escalation

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5.4$0-$5k0.00

Summaryinfo

A vulnerability was found in Linux Kernel up to d1347977661342cb09a304a17701eb2d4aa21dec and classified as problematic. Impacted is the function should_flush_tlb. Executing a manipulation can lead to an unknown weakness. The identification of this vulnerability is CVE-2025-37964. There is no exploit available. It is suggested to upgrade the affected component.

Detailsinfo

A vulnerability classified as problematic was found in Linux Kernel up to d1347977661342cb09a304a17701eb2d4aa21dec. The impact remains unknown. CVE summarizes:

In the Linux kernel, the following vulnerability has been resolved: x86/mm: Eliminate window where TLB flushes may be inadvertently skipped tl;dr: There is a window in the mm switching code where the new CR3 is set and the CPU should be getting TLB flushes for the new mm. But should_flush_tlb() has a bug and suppresses the flush. Fix it by widening the window where should_flush_tlb() sends an IPI. Long Version: === History === There were a few things leading up to this. First, updating mm_cpumask() was observed to be too expensive, so it was made lazier. But being lazy caused too many unnecessary IPIs to CPUs due to the now-lazy mm_cpumask(). So code was added to cull mm_cpumask() periodically[2]. But that culling was a bit too aggressive and skipped sending TLB flushes to CPUs that need them. So here we are again. === Problem === The too-aggressive code in should_flush_tlb() strikes in this window: // Turn on IPIs for this CPU/mm combination, but only // if should_flush_tlb() agrees: cpumask_set_cpu(cpu, mm_cpumask(next)); next_tlb_gen = atomic64_read(&next->context.tlb_gen); choose_new_asid(next, next_tlb_gen, &new_asid, &need_flush); load_new_mm_cr3(need_flush); // ^ After 'need_flush' is set to false, IPIs *MUST* // be sent to this CPU and not be ignored. this_cpu_write(cpu_tlbstate.loaded_mm, next); // ^ Not until this point does should_flush_tlb() // become true! should_flush_tlb() will suppress TLB flushes between load_new_mm_cr3() and writing to 'loaded_mm', which is a window where they should not be suppressed. Whoops. === Solution === Thankfully, the fuzzy "just about to write CR3" window is already marked with loaded_mm==LOADED_MM_SWITCHING. Simply checking for that state in should_flush_tlb() is sufficient to ensure that the CPU is targeted with an IPI. This will cause more TLB flush IPIs. But the window is relatively small and I do not expect this to cause any kind of measurable performance impact. Update the comment where LOADED_MM_SWITCHING is written since it grew yet another user. Peter Z also raised a concern that should_flush_tlb() might not observe 'loaded_mm' and 'is_lazy' in the same order that switch_mm_irqs_off() writes them. Add a barrier to ensure that they are observed in the order they are written.

The advisory is available at git.kernel.org. This vulnerability was named CVE-2025-37964 since 04/16/2025. Technical details are known, but there is no available exploit.

The vulnerability scanner Nessus provides a plugin with the ID 237223 (Debian dsa-5925 : affs-modules-6.1.0-33-4kc-malta-di - security update), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 5.15.183, 6.1.139, 6.6.91, 6.12.29, 6.14.7 or 6.15-rc6 eliminates this vulnerability. Applying the patch 12f703811af043d32b1c8a30001b2fa04d5cd0ac/d41072906abec8bb8e01ed16afefbaa558908c89/d87392094f96e162fa5fa5a8640d70cc0952806f/399ec9ca8fc4999e676ff89a90184ec40031cf59/fea4e317f9e7e1f449ce90dedc27a2d2a95bee5a is able to eliminate this problem. The bugfix is ready for download at git.kernel.org. The best possible mitigation is suggested to be upgrading to the latest version.

The vulnerability is also documented in the databases at Tenable (237223) and CERT Bund (WID-SEC-2025-1114). If you want to get best quality of vulnerability data, you may have to visit VulDB.

Affected

  • Debian Linux
  • Amazon Linux 2
  • Red Hat Enterprise Linux
  • Ubuntu Linux
  • SUSE Linux
  • Oracle Linux
  • SUSE openSUSE
  • Dell Avamar
  • Open Source Linux Kernel
  • Dell NetWorker
  • Dell Secure Connect Gateway

Productinfo

Type

Vendor

Name

Version

License

Website

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔍
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 5.5
VulDB Meta Temp Score: 5.4

VulDB Base Score: 5.5
VulDB Temp Score: 5.3
VulDB Vector: 🔍
VulDB Reliability: 🔍

NVD Base Score: 5.5
NVD Vector: 🔍

CVSSv2info

AVACAuCIA
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VectorComplexityAuthenticationConfidentialityIntegrityAvailability
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VulDB Base Score: 🔍
VulDB Temp Score: 🔍
VulDB Reliability: 🔍

Exploitinginfo

Class: Privilege escalation
CWE: Unknown
CAPEC: 🔍
ATT&CK: 🔍

Physical: Partially
Local: Yes
Remote: Partially

Availability: 🔍
Status: Not defined

EPSS Score: 🔍
EPSS Percentile: 🔍

Price Prediction: 🔍
Current Price Estimation: 🔍

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Nessus ID: 237223
Nessus Name: Debian dsa-5925 : affs-modules-6.1.0-33-4kc-malta-di - security update

Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍

Countermeasuresinfo

Recommended: Upgrade
Status: 🔍

0-Day Time: 🔍

Upgrade: Kernel 5.15.183/6.1.139/6.6.91/6.12.29/6.14.7/6.15-rc6
Patch: 12f703811af043d32b1c8a30001b2fa04d5cd0ac/d41072906abec8bb8e01ed16afefbaa558908c89/d87392094f96e162fa5fa5a8640d70cc0952806f/399ec9ca8fc4999e676ff89a90184ec40031cf59/fea4e317f9e7e1f449ce90dedc27a2d2a95bee5a

Timelineinfo

04/16/2025 🔍
05/20/2025 +34 days 🔍
05/20/2025 +0 days 🔍
12/16/2025 +210 days 🔍

Sourcesinfo

Vendor: kernel.org

Advisory: git.kernel.org
Status: Confirmed

CVE: CVE-2025-37964 (🔍)
GCVE (CVE): GCVE-0-2025-37964
GCVE (VulDB): GCVE-100-309754
CERT Bund: WID-SEC-2025-1114 - Linux Kernel: Mehrere Schwachstellen

Entryinfo

Created: 05/20/2025 18:29
Updated: 12/16/2025 22:26
Changes: 05/20/2025 18:29 (56), 05/25/2025 03:55 (2), 08/10/2025 01:26 (7), 09/27/2025 16:29 (1), 12/14/2025 18:04 (1), 12/16/2025 22:26 (11)
Complete: 🔍
Cache ID: 216::103

If you want to get best quality of vulnerability data, you may have to visit VulDB.

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