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CVE-2025-39773

21
FAUCET Score

CVE-2025-39773 is a Linux kernel vulnerability affecting Debian and other Linux distributions. It involves a soft lockup in the bridge multicast query function, triggered when the multicast_query_interval is set to an excessively large value, causing a timer overflow and an infinite loop. Rated Medium severity (CVSS 5.5), this local vulnerability (AV:L/AC:L/PR:L) can lead to a denial of service (A:H) on the affected system. There is no evidence of active exploitation, public exploit code, or Metasploit/Nuclei modules, though it has garnered some community discussion and media coverage.

Impacted Technologies

VendorProductVersion(s)CPE
>= 2.6.34, < 5.15.190CPE matchmatch criteria
cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
>= 5.16, < 6.1.149CPE matchmatch criteria
cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
>= 6.2, < 6.6.103CPE matchmatch criteria
cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
>= 6.7, < 6.12.44CPE matchmatch criteria
cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
>= 6.13, < 6.16.4CPE matchmatch criteria
cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*

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
0.11%
Probability of exploitation in next 30 days
EPSS Percentile
1.6%
Percentile rank of EPSS score among Peer Group
As of 2026-07-28
Model: v2026.06.15
This CVE's current EPSS score of 0.0011 is in the 10th 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

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

Remediation

Patch Available

Vendor Patches (17)

microsoftpatch availablevia msrc
Product: cbl2 kernel 5.15.186.1-1 on CBL Mariner 2.0Fixed in: 5.15.200.1-1
microsoftpatch availablevia msrc
Product: azl3 kernel 6.6.96.2-2 on Azure Linux 3.0Fixed in: 6.6.104.2-1
microsoftpatch availablevia msrc
Product: 17087-17086Fixed in: 5.15.200.1-1
microsoftpatch availablevia msrc
Product: 20412-17084Fixed in: 6.6.104.2-1
ubuntupatch availablevia ubuntu_usn
Product: linux-xilinx (noble)Fixed in: 6.8.0-1023.24
ubuntupatch availablevia ubuntu_usn
Product: linux-ibm-6.8 (jammy)Fixed in: 6.8.0-1044.44~22.04.1
ubuntupatch availablevia ubuntu_usn
Product: linux-ibm (noble)Fixed in: 6.8.0-1044.44
ubuntupatch availablevia ubuntu_usn
Product: linux-azure-fips (noble)Fixed in: 6.8.0-1046.52+fips1
ubuntupatch availablevia ubuntu_usn
Product: linux-azure (noble)Fixed in: 6.8.0-1046.52
ubuntupatch availablevia ubuntu_usn
Product: linux-azure-6.8 (jammy)Fixed in: 6.8.0-1051.57~22.04.1
redhatend of lifevia redhat_api
Product: Red Hat Enterprise Linux 9Fixed in: kernel-rt
redhatend of lifevia redhat_api
Product: Red Hat Enterprise Linux 7Fixed in: kernel
redhatend of lifevia redhat_api
Product: Red Hat Enterprise Linux 10Fixed in: kernel
redhatend of lifevia redhat_api
Product: Red Hat Enterprise Linux 8Fixed in: kernel
redhatend of lifevia redhat_api
Product: Red Hat Enterprise Linux 7Fixed in: kernel-rt
redhatend of lifevia redhat_api
Product: Red Hat Enterprise Linux 8Fixed in: kernel-rt
redhatend of lifevia redhat_api
Product: Red Hat Enterprise Linux 9Fixed in: kernel

Vendor Advisories (7)

ubuntuUSN-8126-1

Linux kernel (Azure) vulnerabilities

Mar 25, 2026
ubuntuUSN-8074-2

Linux kernel (Azure FIPS) vulnerabilities

Mar 4, 2026
ubuntuUSN-8074-1

Linux kernel (Azure) vulnerabilities

Mar 4, 2026
ubuntuUSN-8052-2

Linux kernel (Xilinx) vulnerabilities

Feb 24, 2026
ubuntuUSN-8028-8

Linux kernel (IBM) vulnerabilities

Feb 24, 2026
redhatCVE-2025-39773Moderate

kernel: net: bridge: fix soft lockup in br_multicast_query_expired()

Sep 11, 2025
microsoft2025-Sep/CVE-2025-39773Moderate

net: bridge: fix soft lockup in br_multicast_query_expired()

Sep 9, 2025

References

cert-portal.siemens.com / productcert/html/ssa-019113.html
cert-portal.siemens.com / productcert/html/ssa-032379.html
cert-portal.siemens.com / productcert/html/ssa-082556.html
git.kernel.org / stable/c/34171b9e53bd1dc264f5556579f2b04f04435c73
Patch
git.kernel.org / stable/c/43e281fde5e76a866a4d10780c35023f16c0e432
Patch
git.kernel.org / stable/c/5bf5fce8a0c2a70d063af778fdb5b27238174cdd
Patch
git.kernel.org / stable/c/96476b043efb86a94f2badd260f7f99c97bd5893
Patch
git.kernel.org / stable/c/bdb19cd0de739870bb3494c815138b9dc30875c4
Patch
git.kernel.org / stable/c/d1547bf460baec718b3398365f8de33d25c5f36f
Patch
lists.debian.org / debian-lts-announce/2025/10/msg00008.html
Third Party Advisory