CVE-2025-21647

HIGH EPSS 18.8%
Published Jan 19, 20251y ago · Modified Jun 17, 20262w ago
7.1 CVSS 3.1
High
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Published Jan 19, 2025 1y ago
Last Modified Jun 17, 2026 2w ago

Description

In the Linux kernel, the following vulnerability has been resolved: sched: sch_cake: add bounds checks to host bulk flow fairness counts Even though we fixed a logic error in the commit cited below, syzbot still managed to trigger an underflow of the per-host bulk flow counters, leading to an out of bounds memory access. To avoid any such logic errors causing out of bounds memory accesses, this commit factors out all accesses to the per-host bulk flow counters to a series of helpers that perform bounds-checking before any increments and decrements. This also has the benefit of improving readability by moving the conditional checks for the flow mode into these helpers, instead of having them spread out throughout the code (which was the cause of the original logic error). As part of this change, the flow quantum calculation is consolidated into a helper function, which means that the dithering applied to the ost load scaling is now applied both in the DRR rotation and when a sparse flow's quantum is first initiated. The only user-visible effect of this is that the maximum packet size that can be sent while a flow stays sparse will now vary with +/- one byte in some cases. This should not make a noticeable difference in practice, and thus it's not worth complicating the code to preserve the old behaviour.

CVSS Details

Base Score
7.1
Exploitability
1.8
Impact
5.2
Vector string
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H
Attack Vector Local
Attack Complexity Low
Privileges Required Low
User Interaction None
Scope Unchanged
Confidentiality High
Integrity None
Availability High

Threat Intelligence

EPSS Exploit Probability
18.8% percentile
Exploit & Patch Status
No Known Exploit
Patch Available

Weaknesses 1

CWE-125 Out-of-bounds Read Memory Safety

Affected Products 15

VendorProductVersionRange
linuxlinux_kernel*≥5.4.284  –  <5.4.291
linuxlinux_kernel*≥5.10.226  –  <5.10.235
linuxlinux_kernel*≥5.15.167  –  <5.15.179
linuxlinux_kernel*≥6.1.110  –  <6.1.125
linuxlinux_kernel*≥6.6.51  –  <6.6.72
linuxlinux_kernel*≥6.10.10  –  <6.11
linuxlinux_kernel*≥6.11.1  –  <6.12.10
linuxlinux_kernel6.11any
linuxlinux_kernel6.11any
linuxlinux_kernel6.13any
linuxlinux_kernel6.13any
linuxlinux_kernel6.13any
linuxlinux_kernel6.13any
linuxlinux_kernel6.13any
linuxlinux_kernel6.13any

References 11

  • cert-portal.siemens.com https://cert-portal.siemens.com/productcert/html/ssa-265688.html
  • cert-portal.siemens.com https://cert-portal.siemens.com/productcert/html/ssa-503939.html
  • git.kernel.org https://git.kernel.org/stable/c/27202e2e8721c3b23831563c36ed5ac7818641ba
    Patch
  • git.kernel.org https://git.kernel.org/stable/c/44fe1efb4961c1a5ccab16bb579dfc6b308ad58b
    Patch
  • git.kernel.org https://git.kernel.org/stable/c/737d4d91d35b5f7fa5bb442651472277318b0bfd
    Patch
  • git.kernel.org https://git.kernel.org/stable/c/91bb18950b88f955838ec0c1d97f74d135756dc7
    Patch
  • git.kernel.org https://git.kernel.org/stable/c/a777e06dfc72bed73c05dcb437d7c27ad5f90f3f
    Patch
  • git.kernel.org https://git.kernel.org/stable/c/b1a1743aaa4906c41c426eda97e2e2586f79246d
    Patch
  • git.kernel.org https://git.kernel.org/stable/c/bb0245fa72b783cb23a9949c5048781341e91423
    Patch
  • lists.debian.org https://lists.debian.org/debian-lts-announce/2025/03/msg00001.html
  • lists.debian.org https://lists.debian.org/debian-lts-announce/2025/05/msg00030.html

Remediation

  • git.kernel.org https://git.kernel.org/stable/c/27202e2e8721c3b23831563c36ed5ac7818641ba
    Patch
  • git.kernel.org https://git.kernel.org/stable/c/44fe1efb4961c1a5ccab16bb579dfc6b308ad58b
    Patch
  • git.kernel.org https://git.kernel.org/stable/c/737d4d91d35b5f7fa5bb442651472277318b0bfd
    Patch
  • git.kernel.org https://git.kernel.org/stable/c/91bb18950b88f955838ec0c1d97f74d135756dc7
    Patch
  • git.kernel.org https://git.kernel.org/stable/c/a777e06dfc72bed73c05dcb437d7c27ad5f90f3f
    Patch
  • git.kernel.org https://git.kernel.org/stable/c/b1a1743aaa4906c41c426eda97e2e2586f79246d
    Patch
  • git.kernel.org https://git.kernel.org/stable/c/bb0245fa72b783cb23a9949c5048781341e91423
    Patch