Read the docs
TI-2025-41788 Aliases CVE-2025-68211GHSA-qhqr-mc3h-hmjp

ksm: use range-walk function to jump over holes in scan_get_next_rmap_item

Priority LOW 24Published · Updated

Key facts

Attack vector
Local
Privileges required
Low
User interaction
None
Attack complexity
Low
Impact type
—
Confidentiality · integrity · availability
None · None · High
Fix status
Partial Red Hat: 15 fixed, 4 without a fix

Attack profile from CVSS 3.1 · NVD. Fix status from CNA and Red Hat.

Summary

In the Linux kernel, the following vulnerability has been resolved: ksm: use range-walk function to jump over holes in scan_get_next_rmap_item Currently, scan_get_next_rmap_item() walks every page address in a VMA to locate mergeable pages. This becomes highly inefficient when scanning large virtual memory areas that contain mostly unmapped regions, causing ksmd to use large amount of cpu without deduplicating much pages. This patch replaces the per-address lookup with a range walk using walk_page_range(). The range walker allows KSM to skip over entire unmapped holes in a VMA, avoiding unnecessary lookups. This problem was previously discussed in [1]. Consider the following test program which creates a 32 TiB mapping in the virtual address space but only populates a single page: #include <unistd.h> #include <stdio.h> #include <sys/mman.h> /* 32 TiB */ const size_t size = 32ul * 1024 * 1024 * 1024 * 1024; int main() { char *area = mmap(NULL, size, PROT_READ | PROT_WRITE, MAP_NORESERVE | MAP_PRIVATE | MAP_ANON, -1, 0); if (area == MAP_FAILED) { perror("mmap() failed\n"); return -1; } /* Populate a single page such that we get an anon_vma. */ *area = 0; /* Enable KSM. */ madvise(area, size, MADV_MERGEABLE); pause(); return 0; } $ ./ksm-sparse & $ echo 1 > /sys/kernel/mm/ksm/run Without this patch ksmd uses 100% of the cpu for a long time (more then 1 hour in my test machine) scanning all the 32 TiB virtual address space that contain only one mapped page. This makes ksmd essentially deadlocked not able to deduplicate anything of value. With this patch ksmd walks only the one mapped page and skips the rest of the 32 TiB virtual address space, making the scan fast using little cpu.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00147 3rd percentileScored 2026-11-07
Fix Partial Linux (Linux): 5.10.249, 5.15.199, 6.1.161 +4Red Hat: 3 advisoriesRed Hat: 15 fixed, 4 without a fix

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
None
Automatable
No
Technical impact
Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
LinuxLinux2.6.32 and later5.10.249, 5.15.199, 6.1.161, 6.6.121, 6.12.59, 6.17.9, 6.18Patch availableCNA
  • Linux VendorLinux Affected 2.6.32 and later Fixed in 5.10.249, 5.15.199, 6.1.161, 6.6.121, 6.12.59, 6.17.9, 6.18 Patch available CNA

CPE configurations NVD · 6

CPEVersionsRoleVendor
cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*2.6.32 to before 5.10.249; 5.11 to before 5.15.199; 5.16 to before 6.1.161; 6.2 to before 6.6.121; 6.7 to before 6.12.59; 6.13 to before 6.17.9VulnerableLinux
cpe:2.3:o:linux:linux_kernel:6.18:rc1:*:*:*:*:*:*6.18 rc1VulnerableLinux
cpe:2.3:o:linux:linux_kernel:6.18:rc2:*:*:*:*:*:*6.18 rc2VulnerableLinux
cpe:2.3:o:linux:linux_kernel:6.18:rc3:*:*:*:*:*:*6.18 rc3VulnerableLinux
cpe:2.3:o:linux:linux_kernel:6.18:rc4:*:*:*:*:*:*6.18 rc4VulnerableLinux
cpe:2.3:o:linux:linux_kernel:6.18:rc5:*:*:*:*:*:*6.18 rc5VulnerableLinux
  • cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* Versions 2.6.32 to before 5.10.249; 5.11 to before 5.15.199; 5.16 to before 6.1.161; 6.2 to before 6.6.121; 6.7 to before 6.12.59; 6.13 to before 6.17.9 Vulnerable ·Linux
  • cpe:2.3:o:linux:linux_kernel:6.18:rc1:*:*:*:*:*:* Versions 6.18 rc1 Vulnerable ·Linux
  • cpe:2.3:o:linux:linux_kernel:6.18:rc2:*:*:*:*:*:* Versions 6.18 rc2 Vulnerable ·Linux
  • cpe:2.3:o:linux:linux_kernel:6.18:rc3:*:*:*:*:*:* Versions 6.18 rc3 Vulnerable ·Linux
  • cpe:2.3:o:linux:linux_kernel:6.18:rc4:*:*:*:*:*:* Versions 6.18 rc4 Vulnerable ·Linux
  • cpe:2.3:o:linux:linux_kernel:6.18:rc5:*:*:*:*:*:* Versions 6.18 rc5 Vulnerable ·Linux

Remediation

  • Fix · CNA Linux (Linux) Fixed in 5.10.249, 5.15.199, 6.1.161, 6.6.121, 6.12.59, 6.17.9, 6.18

Red Hat 3 advisories

  • RHSA-2026:62568 Released 2026-09-02 · Red Hat rating Important
    kernel security, bug fix, and enhancement update
    • Red Hat CodeReady Linux Builder EUS (v.9.6) kernel-tools-libs-devel-5.14.0-570.138.1.el9_6, libperf-5.14.0-570.138.1.el9_6
    • Red Hat Enterprise Linux AppStream EUS (v.9.6) kernel-64k-debug-devel-5.14.0-570.138.1.el9_6, kernel-64k-debug-devel-matched-5.14.0-570.138.1.el9_6, kernel-64k-devel-5.14.0-570.138.1.el9_6 +12
    • Red Hat Enterprise Linux BaseOS EUS (v.9.6) kernel-5.14.0-570.138.1.el9_6, kernel-64k-5.14.0-570.138.1.el9_6, kernel-64k-core-5.14.0-570.138.1.el9_6 +28
    • Red Hat Enterprise Linux Real Time EUS (v.9.6) kernel-rt-5.14.0-570.138.1.el9_6, kernel-rt-64k-5.14.0-570.138.1.el9_6, kernel-rt-64k-core-5.14.0-570.138.1.el9_6 +21
    • Red Hat Enterprise Linux Real Time for NFV EUS (v.9.6) kernel-rt-5.14.0-570.138.1.el9_6, kernel-rt-core-5.14.0-570.138.1.el9_6, kernel-rt-debug-5.14.0-570.138.1.el9_6 +11
  • RHSA-2026:59723 Released 2026-08-26 · Red Hat rating Important
    kernel security, bug fix, and enhancement update
    • Red Hat Enterprise Linux AppStream (v. 9) kernel-64k-debug-devel-5.14.0-687.42.1.el9_8, kernel-64k-debug-devel-matched-5.14.0-687.42.1.el9_8, kernel-64k-devel-5.14.0-687.42.1.el9_8 +12
    • Red Hat Enterprise Linux BaseOS (v. 9) kernel-5.14.0-687.42.1.el9_8, kernel-64k-5.14.0-687.42.1.el9_8, kernel-64k-core-5.14.0-687.42.1.el9_8 +28
    • Red Hat Enterprise Linux CodeReady Linux Builder (v. 9) kernel-tools-libs-devel-5.14.0-687.42.1.el9_8, libperf-5.14.0-687.42.1.el9_8
    • Red Hat Enterprise Linux Real Time (v. 9) kernel-rt-5.14.0-687.42.1.el9_8, kernel-rt-64k-5.14.0-687.42.1.el9_8, kernel-rt-64k-core-5.14.0-687.42.1.el9_8 +21
    • Red Hat Enterprise Linux Real Time for NFV (v. 9) kernel-rt-5.14.0-687.42.1.el9_8, kernel-rt-core-5.14.0-687.42.1.el9_8, kernel-rt-debug-5.14.0-687.42.1.el9_8 +9
  • RHSA-2026:49211 Released 2026-07-31 · Red Hat rating Important
    kernel security, bug fix, and enhancement update
    • Red Hat Enterprise Linux AppStream (v. 10) kernel-64k-debug-devel-6.12.0-211.42.1.el10_2, kernel-64k-debug-devel-matched-6.12.0-211.42.1.el10_2, kernel-64k-devel-6.12.0-211.42.1.el10_2 +12
    • Red Hat Enterprise Linux BaseOS (v. 10) kernel-6.12.0-211.42.1.el10_2, kernel-64k-6.12.0-211.42.1.el10_2, kernel-64k-core-6.12.0-211.42.1.el10_2 +29
    • Red Hat Enterprise Linux CodeReady Linux Builder (v. 10) kernel-tools-libs-devel-6.12.0-211.42.1.el10_2, libperf-6.12.0-211.42.1.el10_2
    • Red Hat Enterprise Linux Real Time (v. 10) kernel-rt-6.12.0-211.42.1.el10_2, kernel-rt-64k-6.12.0-211.42.1.el10_2, kernel-rt-64k-core-6.12.0-211.42.1.el10_2 +21
    • Red Hat Enterprise Linux Real Time for NFV (v. 10) kernel-rt-6.12.0-211.42.1.el10_2, kernel-rt-core-6.12.0-211.42.1.el10_2, kernel-rt-debug-6.12.0-211.42.1.el10_2 +9

Vendor assessments

Red Hat

Red Hat rating: Moderate. Red Hat's page for this CVE →

ProductStatusPlan or fix
Red Hat Enterprise Linux 6AffectedNo fix planned: Out of support scope
Red Hat Enterprise Linux 7AffectedNo fix yet: Fix deferred
Red Hat Enterprise Linux 8AffectedNo fix yet: Fix deferred
Red Hat Enterprise Linux 9AffectedNo fix yet: Fix deferred
Red Hat CodeReady Linux Builder EUS (v.9.6)Fixed RHSA-2026:62568
Red Hat Enterprise Linux AppStream (v. 10)Fixed RHSA-2026:49211
Red Hat Enterprise Linux AppStream (v. 9)Fixed RHSA-2026:59723
Red Hat Enterprise Linux AppStream EUS (v.9.6)Fixed RHSA-2026:62568
Red Hat Enterprise Linux BaseOS (v. 10)Fixed RHSA-2026:49211
Red Hat Enterprise Linux BaseOS (v. 9)Fixed RHSA-2026:59723
Red Hat Enterprise Linux BaseOS EUS (v.9.6)Fixed RHSA-2026:62568
Red Hat Enterprise Linux CodeReady Linux Builder (v. 10)Fixed RHSA-2026:49211
Red Hat Enterprise Linux CodeReady Linux Builder (v. 9)Fixed RHSA-2026:59723
Red Hat Enterprise Linux Real Time (v. 10)Fixed RHSA-2026:49211
Red Hat Enterprise Linux Real Time (v. 9)Fixed RHSA-2026:59723
Red Hat Enterprise Linux Real Time EUS (v.9.6)Fixed RHSA-2026:62568
Red Hat Enterprise Linux Real Time for NFV (v. 10)Fixed RHSA-2026:49211
Red Hat Enterprise Linux Real Time for NFV (v. 9)Fixed RHSA-2026:59723
Red Hat Enterprise Linux Real Time for NFV EUS (v.9.6)Fixed RHSA-2026:62568

Timeline

  1. 2026-10-02 Threatist record created from CVE-2025-68211
  2. 2026-10-03 Alias added: GHSA-qhqr-mc3h-hmjp
  3. 2026-10-29 Affected versions changed · Red Hat

References

Patch 7

  • TI-2025-26358 tls: fix handling of zero-length records on the rx_list KEVCVSS 3.1CRITICAL 9.8
  • TI-2026-38352 netfilter: bridge: make ebt_snat ARP rewrite writable KEVCVSS 3.1HIGH 8.8
  • TI-2013-05264 The (1) get_user and (2) put_user API functions in the Linux kernel before 3.5.5 on the… KEVCVSS 3.1HIGH 8.8
  • TI-2022-00125 Integer overflow in kernel KEVCVSS 3.1HIGH 8.4
  • TI-2013-01864 The perf_swevent_init function in kernel/events/core.c in the Linux kernel before 3.8.9… KEVCVSS 3.1HIGH 8.4
  • TI-2021-05514 Heap Out-Of-Bounds Write in Netfilter IP6T_SO_SET_REPLACE KEVCVSS 3.1HIGH 8.3
See all 15278 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences