x86/mm: Eliminate window where TLB flushes may be inadvertently skipped
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.
- Published
- May 20, 2025
- Updated
- Sep 8, 2026
- EPSS
- 0.2% · 9th percentile
- CWE
- —
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Report tools
Action score
22
Monitor
Low priority for now.
- CVSS
- 22 / 40 · 5.5 / 10
- CISA KEV
- 0 / 30 · Not listed
- EPSS
- 0 / 30 · 0.2%
CNA vs NVD score
- NVD
- 5.5
- CNA · Linux
- 7.8
- 2.3 point gap
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.
Noroxi analysis
No Noroxi analysis for this record yet
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We use this product, ask for helpAffected systems
| Vendor | Product | CPE |
|---|---|---|
| linux | linux kernel | cpe:2.3:o:linux:linux_kernel |
| debian | debian linux | cpe:2.3:o:debian:debian_linux |
Affected versions
NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.
- debian debian linux11.0
- linux linux kernel6.1.129 and later · before 6.1.139
- linux linux kernel6.6.79 and later · before 6.6.91
- linux linux kernel5.15.179 and later · before 5.15.183
- linux linux kernel6.13.4 and later · before 6.14.7
- linux linux kernel6.12.16 and later · before 6.12.29
- linux linux kernel6.15
Versions reported by the vendor
Affected version ranges reported by the assigning authority (Linux). Independent of NVD's CPE analysis and usually ahead of it.
Linux Linux
- d1347977661342cb09a304a17701eb2d4aa21dec, 6.14affected
- 848b5815177582de0e1d0118725378e0fbadca20 and later · before 12f703811af043d32b1c8a30001b2fa04d5cd0acaffected · git
- b47002ed65ade940839b7f439ff4a194e7d5ec28 and later · before 02ad4ce144bd27f71f583f667fdf3b3ba0753477affected · git
- a04fe3bfc71e28009e20357b79df1e8ef7c9d600 and later · before d41072906abec8bb8e01ed16afefbaa558908c89affected · git
- 3dbe889a1b829b4c07e0836ff853fe649e51ce4f and later · before d87392094f96e162fa5fa5a8640d70cc0952806faffected · git
- 6db2526c1d694c91c6e05e2f186c085e9460f202 and later · before 399ec9ca8fc4999e676ff89a90184ec40031cf59affected · git
- 6db2526c1d694c91c6e05e2f186c085e9460f202 and later · before fea4e317f9e7e1f449ce90dedc27a2d2a95bee5aaffected · git
- 5.15.179 and later · before 5.15.183affected · semver
- 6.1.129 and later · before 6.1.139affected · semver
- 6.6.79 and later · before 6.6.91affected · semver
Package-level exposure
OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.
| Ecosystem | Package | Affected range | Fix |
|---|---|---|---|
| Debian:12 | linux | before 6.1.140-1 | 6.1.140-1 |
| Debian:13 | linux | before 6.12.29-1 | 6.12.29-1 |
Same product
linux: all recordsOther highest-scoring records for the same primary product.
- CVE-2022-0847A flaw was found in the way the "flags" member of the new pipe buffer structure was lacking proper initialization in copy_page_to_iter_pipe KEV89Now
- CVE-2021-22555Heap Out-Of-Bounds Write in Netfilter IP6T_SO_SET_REPLACEKEV85Now
- CVE-2016-5195Race condition in mm/gup.c in the Linux kernel 2.x through 4.x before 4.8.3 allows local users to gain privileges by leveraging incorrect haKEV83Now
- CVE-2019-13272In the Linux kernel before 5.1.17, ptrace_link in kernel/ptrace.c mishandles the recording of the credentials of a process that wants to creKEV77This week
- CVE-2013-6282The (1) get_user and (2) put_user API functions in the Linux kernel before 3.5.5 on the v6k and v7 ARM platforms do not validate certain addKEV77This week
- CVE-2013-2094The perf_swevent_init function in kernel/events/core.c in the Linux kernel before 3.8.9 uses an incorrect integer data type, which allows loKEV77This week
Remediation
Which version to upgrade to
Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.
| Product / package | Fixed version | Source |
|---|---|---|
| Linux Linux | 02ad4ce144bd27f71f583f667fdf3b3ba0753477 | Vendor (CNA) |
| Linux Linux | 12f703811af043d32b1c8a30001b2fa04d5cd0ac | Vendor (CNA) |
| Linux Linux | 399ec9ca8fc4999e676ff89a90184ec40031cf59 | Vendor (CNA) |
| Linux Linux | 5.15.183 | Vendor (CNA) |
| Linux Linux | 6.1.139 | Vendor (CNA) |
| Linux Linux | 6.12.29 | Vendor (CNA) |
| Linux Linux | 6.14 | Vendor (CNA) |
| Linux Linux | 6.6.91 | Vendor (CNA) |
| Linux Linux | d41072906abec8bb8e01ed16afefbaa558908c89 | Vendor (CNA) |
| Linux Linux | d87392094f96e162fa5fa5a8640d70cc0952806f | Vendor (CNA) |
| Linux Linux | fea4e317f9e7e1f449ce90dedc27a2d2a95bee5a | Vendor (CNA) |
| debian:linux | 6.1.140-1 · Debian:12 | Package registry (OSV) |
Exploit status
No known public exploit
No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.
Research context
For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.
Timeline
From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.
No dated events beyond publication.
FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).
Patch and commit links
Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.
No commit or PR link among the references.
Credits
All researchersFinders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.
No credits in the CNA record.
Variant candidates
Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.
No nightly-computed relations.
Chain candidates
An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.
—
Bug bounty scope
No known public program.
Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).
Technical details
Attack conditions
- Someone with local access to the system can trigger it.
- A low-privileged account is enough.
- No user action is required.
- No special conditions are required; it is repeatable.
If successful
- Confidentiality
- none
- Integrity
- none
- Availability
- high · the service can be disrupted
- Attack vector
- Local
- Attack complexity
- Low
- Privileges required
- Low
- User interaction
- None
- Scope
- Unchanged
- Confidentiality impact
- None
- Integrity impact
- None
- Availability impact
- High
Weakness class (CWE)
—
CVSS vector
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
nvd-primary
Attack context
MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.
MITRE has no CAPEC/ATT&CK mapping for this CWE.
Change log
- Fix✗ → ✓
For records you follow, these changes also arrive as notifications. →
References
- git.kernel.org/stable/c/02ad4ce144bd27f71f583f667fdf3b3ba0753477
- git.kernel.org/stable/c/12f703811af043d32b1c8a30001b2fa04d5cd0ac
- git.kernel.org/stable/c/399ec9ca8fc4999e676ff89a90184ec40031cf59
- git.kernel.org/stable/c/d41072906abec8bb8e01ed16afefbaa558908c89
- git.kernel.org/stable/c/d87392094f96e162fa5fa5a8640d70cc0952806f
- git.kernel.org/stable/c/fea4e317f9e7e1f449ce90dedc27a2d2a95bee5a
- lists.debian.org/debian-lts-announce/2025/08/msg00010.html
- cert-portal.siemens.com/productcert/html/ssa-019113.html
Vendor advisories and official records. Exploit/PoC links are deliberately left out.