netem: Update sch->q.qlen before qdisc_tree_reduce_backlog()
Priority LOW 36CWE-416Published · Updated
Key facts
- Attack vector
- Local
- Privileges required
- Low
- User interaction
- None
- Attack complexity
- Low
- Impact type
- Code execution
- Confidentiality · integrity · availability
- High · High · High
- Fix status
- Partial Red Hat: 1 without a fix
Attack profile from CVSS 3.1 · CNA. Fix status from CNA and Red Hat. Impact type from CWE-416 and the CVSS impact.
Summary
In the Linux kernel, the following vulnerability has been resolved: netem: Update sch->q.qlen before qdisc_tree_reduce_backlog() qdisc_tree_reduce_backlog() notifies parent qdisc only if child qdisc becomes empty, therefore we need to reduce the backlog of the child qdisc before calling it. Otherwise it would miss the opportunity to call cops->qlen_notify(), in the case of DRR, it resulted in UAF since DRR uses ->qlen_notify() to maintain its active list.
Why it matters now
Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00304 23rd percentileScored 2026-11-07
Fix Partial Linux (Linux): 5.4.291, 5.10.235, 5.15.179 +5Red Hat: 1 without a fix
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- None
- Automatable
- No
- Technical impact
- Total
The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| Linux | Linux | 5.4.288 to before 5.4.291; 5.10.232 to before 5.10.235; 5.15.175 to before 5.15.179; 6.1.121 to before 6.1.129; 6.6.67 to before 6.6.78; 6.12.6 to before 6.12.14 | 5.4.291, 5.10.235, 5.15.179, 6.1.129, 6.6.78, 6.12.14 | Patch available | CNA |
| Linux | Linux | 6.13 and later | 5.4.291, 5.10.235, 5.15.179, 6.1.129, 6.6.78, 6.12.14, 6.13.3, 6.14 | Patch available | CNA |
- Linux VendorLinux Affected 5.4.288 to before 5.4.291; 5.10.232 to before 5.10.235; 5.15.175 to before 5.15.179; 6.1.121 to before 6.1.129; 6.6.67 to before 6.6.78; 6.12.6 to before 6.12.14 Fixed in 5.4.291, 5.10.235, 5.15.179, 6.1.129, 6.6.78, 6.12.14 Patch available CNA
- Linux VendorLinux Affected 6.13 and later Fixed in 5.4.291, 5.10.235, 5.15.179, 6.1.129, 6.6.78, 6.12.14, 6.13.3, 6.14 Patch available CNA
CPE configurations NVD · 2
| CPE | Versions | Role | Vendor |
|---|---|---|---|
| cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* | 5.4.288 to before 5.4.291; 5.10.232 to before 5.10.235; 5.15.175 to before 5.15.179; 6.1.121 to before 6.1.129; 6.6.67 to before 6.6.78; 6.12.6 to before 6.12.14; 6.13 to before 6.13.3 | Vulnerable | Linux |
| cpe:2.3:o:linux:linux_kernel:6.14:rc1:*:*:*:*:*:* | 6.14 rc1 | Vulnerable | Linux |
- cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* Versions 5.4.288 to before 5.4.291; 5.10.232 to before 5.10.235; 5.15.175 to before 5.15.179; 6.1.121 to before 6.1.129; 6.6.67 to before 6.6.78; 6.12.6 to before 6.12.14; 6.13 to before 6.13.3 Vulnerable ·Linux
- cpe:2.3:o:linux:linux_kernel:6.14:rc1:*:*:*:*:*:* Versions 6.14 rc1 Vulnerable ·Linux
Remediation
- Fix · CNA Linux (Linux) Fixed in 5.4.291, 5.10.235, 5.15.179, 6.1.129, 6.6.78, 6.12.14
- Fix · CNA Linux (Linux) Fixed in 5.4.291, 5.10.235, 5.15.179, 6.1.129, 6.6.78, 6.12.14, 6.13.3, 6.14
Vendor assessments
Red Hat
Red Hat rating: Moderate. Red Hat's page for this CVE →
| Product | Status | Plan or fix |
|---|---|---|
| Red Hat Enterprise Linux 6 | Affected | No fix planned: Out of support scope |
Not affected: 4 products
- Red Hat Enterprise Linux 10
- Red Hat Enterprise Linux 7
- Red Hat Enterprise Linux 8
- Red Hat Enterprise Linux 9
Timeline
- 2026-10-02 Threatist record created from CVE-2025-21703
- 2026-10-03 Alias added: GHSA-cg86-m5xc-jqrm
References
Patch 8
- https://git.kernel.org/stable/c/e395fec75ac2dbffc99b4bce57b7f1f3c5449f2c
- https://git.kernel.org/stable/c/7f31d74fcc556a9166b1bb20515542de7bb939d1
- https://git.kernel.org/stable/c/98a2c685293aae122f688cde11d9334dddc5d207
- https://git.kernel.org/stable/c/7b79ca9a1de6a428d486ff52fb3d602321c08f55
- https://git.kernel.org/stable/c/1f8e3f4a4b8b90ad274dfbc66fc7d55cb582f4d5
- https://git.kernel.org/stable/c/6312555249082d6d8cc5321ff725df05482d8b83
- https://git.kernel.org/stable/c/839ecc583fa00fab785fde1c85a326743657fd32
- https://git.kernel.org/stable/c/638ba5089324796c2ee49af10427459c2de35f71
More Linux Kernel vulnerabilities
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- 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
Sources
- CVE-2025-21703 · CVE Program
- CVE-2025-21703 · NVD
- FIRST EPSS
- GHSA-cg86-m5xc-jqrm · GitHub Advisory Database · CC BY 4.0
- CVE-2025-21703 · Red Hat security data · CC BY 4.0
This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences