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CVE-2025-39677

20
FAUCET Score

CVE-2025-39677 is a vulnerability in the Linux kernel's networking scheduler, specifically affecting the hhf, fq, fq_codel, and fq_pie qdiscs. It stems from incorrect backlog accounting when adjusting qdisc limits, leading to an underflow in the parent tbf qdisc's backlog. This issue is rated Medium severity (CVSS 5.5) with a local attack vector, low attack complexity, and high impact on availability. There is no known active exploitation, public exploit code, or significant community discussion surrounding this vulnerability.

Impacted Technologies

VendorProductVersion(s)CPE
>= 3.5, < 6.16.4CPE matchmatch criteria
cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
6.17CPE matchmatch criteria
cpe:2.3:o:linux:linux_kernel:6.17:rc1:*:*:*:*:*:*
6.17CPE matchmatch criteria
cpe:2.3:o:linux:linux_kernel:6.17:rc2:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

5.5MEDIUM

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Attack Vector
LOCAL
Attack Complexity
LOW
Privileges Required
LOW
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
NONE
Integrity Impact
NONE
Availability Impact
HIGH
Exploitability Score
1.8
Impact Score
3.6
CvssVersion
3.1

Exploit Intelligence

EPSS Score
0.13%
Probability of exploitation in next 30 days
EPSS Percentile
2.8%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.0013 is in the 19th percentile among its peer group of 15,940 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.0 Reddit, 0.0 Bluesky, 0.0 Mastodon, and 0.1 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.1 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Vendor Patches (7)

redhatvendor investigatingvia redhat_api
Product: Red Hat Enterprise Linux 10Fixed in: kernel
redhatvendor investigatingvia redhat_api
Product: Red Hat Enterprise Linux 7Fixed in: kernel
redhatvendor investigatingvia redhat_api
Product: Red Hat Enterprise Linux 7Fixed in: kernel-rt
redhatvendor investigatingvia redhat_api
Product: Red Hat Enterprise Linux 8Fixed in: kernel
redhatvendor investigatingvia redhat_api
Product: Red Hat Enterprise Linux 8Fixed in: kernel-rt
redhatvendor investigatingvia redhat_api
Product: Red Hat Enterprise Linux 9Fixed in: kernel
redhatvendor investigatingvia redhat_api
Product: Red Hat Enterprise Linux 9Fixed in: kernel-rt

Vendor Advisories (2)

microsoft2025-Sep/CVE-2025-39677Moderate

net/sched: Fix backlog accounting in qdisc_dequeue_internal

Sep 9, 2025
redhatCVE-2025-39677Moderate

kernel: net/sched: Fix backlog accounting in qdisc_dequeue_internal

Sep 5, 2025

References

git.kernel.org / stable/c/52bf272636bda69587952b35ae97690b8dc89941
Patch
git.kernel.org / stable/c/a225f44d84b8900d679c5f5a9ea46fe9c0cc7802
Patch