CVE-2026-98012

net/sched: sfq: clamp quantum in change path

State: Published
Severity: Not scored
Published: Sep 25, 2026
Updated: Oct 19, 2026
Reserved: Sep 25, 2026

Description

In the Linux kernel, the following vulnerability has been resolved:

net/sched: sfq: clamp quantum in change path

sfq_change() accepts any non-negative quantum (only rejects (int)ctl->quantum < 0). With a crafted size table qdisc_pkt_len reaches ~2 GiB, so quantum=1 makes the deficit-refill loop spin ~2^31 times under the qdisc lock (a soft lockup / denial of service).

Add max(256U, ...) matching fq_codel_change(). Reject quantum > 1<<20 with -EINVAL, matching fq_codel_change() and the init clamp.

Conditions to recreate the bug: CONFIG_NET_SCH_SFQ=y. Requires CAP_NET_ADMIN (namespace-local via unshare -Urn suffices).

tc qdisc add dev dummy0 root sfq tc qdisc change dev dummy0 root sfq quantum 1 stab data 32768 size_log 15 cell_log 0

Scores

The record has no CVSS score.

Weaknesses

The record names no weakness.

Affected Products

Product	Versions
LinuxLinux	4919649699c5f4dbae08b8e2ed536fc9d6c3c2aa to before 4117c528b2de5fdc3e4a7e3626815b616a635cdcAffected 548cf048b426729a7a1fa6acd1271c010c9a7380 to before f82fa6f10d4a69322cad0f7a4aa523ce6292a5a0Affected c49ac48fac51a6a54efd5963954d02bacf075085 to before 0692ce5a528df450d64e9f819054177e9d91076fAffected 58ae7465f0e7113d45aa88a66bf2d203c71c195e to before e4192bcf83aaab02129644ddf4656fd86e93751fAffected 82bd38bd5467ece1ee274b493f51326cf5220a5a to before f3820dce042a673fcb28cc31c87ee14257e21a17Affected e4650d7ae4252f67e997a632adfae0dd74d3a99a to before 534cd7ecbbc6e8a974f4003a5c1557439c6e0a72Affected e4650d7ae4252f67e997a632adfae0dd74d3a99a to before e6c1cb728e389354203a72bc77464c222a247aebAffected e4650d7ae4252f67e997a632adfae0dd74d3a99a to before fb9f88a33c516ea5c0bcd9a22ca288b246b34567Affected 843cacb88f42f426973f1ed11c6fb562558efb27Affected 5.10.239 to before 5.10.271Affected 5.15.186 to before 5.15.222Affected 6.1.129 to before 6.1.189Affected 6.6.76 to before 6.6.158Affected 6.12.13 to before 6.12.111Affected 5.4.297 to before 5.5Affected
LinuxLinux	6.13Affected before 6.13Not affected 5.10.271 through 5.10.Not affected 5.15.222 through 5.15.Not affected 6.1.189 through 6.1.Not affected 6.6.158 through 6.6.Not affected 6.12.111 through 6.12.Not affected 6.18.53 through 6.18.Not affected 7.2.7 through 7.2.*Not affected 7.3 and laterNot affected

Product

Versions

LinuxLinux

4919649699c5f4dbae08b8e2ed536fc9d6c3c2aa to before 4117c528b2de5fdc3e4a7e3626815b616a635cdcAffected
548cf048b426729a7a1fa6acd1271c010c9a7380 to before f82fa6f10d4a69322cad0f7a4aa523ce6292a5a0Affected
c49ac48fac51a6a54efd5963954d02bacf075085 to before 0692ce5a528df450d64e9f819054177e9d91076fAffected
58ae7465f0e7113d45aa88a66bf2d203c71c195e to before e4192bcf83aaab02129644ddf4656fd86e93751fAffected
82bd38bd5467ece1ee274b493f51326cf5220a5a to before f3820dce042a673fcb28cc31c87ee14257e21a17Affected
e4650d7ae4252f67e997a632adfae0dd74d3a99a to before 534cd7ecbbc6e8a974f4003a5c1557439c6e0a72Affected
e4650d7ae4252f67e997a632adfae0dd74d3a99a to before e6c1cb728e389354203a72bc77464c222a247aebAffected
e4650d7ae4252f67e997a632adfae0dd74d3a99a to before fb9f88a33c516ea5c0bcd9a22ca288b246b34567Affected
843cacb88f42f426973f1ed11c6fb562558efb27Affected
5.10.239 to before 5.10.271Affected
5.15.186 to before 5.15.222Affected
6.1.129 to before 6.1.189Affected
6.6.76 to before 6.6.158Affected
6.12.13 to before 6.12.111Affected
5.4.297 to before 5.5Affected

LinuxLinux

6.13Affected
before 6.13Not affected
5.10.271 through 5.10.*Not affected
5.15.222 through 5.15.*Not affected
6.1.189 through 6.1.*Not affected
6.6.158 through 6.6.*Not affected
6.12.111 through 6.12.*Not affected
6.18.53 through 6.18.*Not affected
7.2.7 through 7.2.*Not affected
7.3 and laterNot affected

References

Every record here comes from the CVE Program’s CVE List. © 1999–2026 The MITRE Corporation. CVE is a registered trademark of The MITRE Corporation. The records are reproduced under the CVE Program terms of use.