Linux Kernel up to 7.3-rc1/7.3-rc2 fq net/sched/sch_fq.c fq_change TCA_FQ_QUANTUM/TCA_FQ_INITIAL_QUANTUM input validation

CVSS Meta Temp Score
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4.2$0-$5k0.00

Summaryinfo

A vulnerability was found in Linux Kernel up to 7.3-rc1/7.3-rc2 and classified as problematic. Affected by this issue is the function fq_change of the file net/sched/sch_fq.c of the component fq. Such manipulation of the argument TCA_FQ_QUANTUM/TCA_FQ_INITIAL_QUANTUM leads to input validation. This vulnerability is referenced as CVE-2026-90050. The attack can only be performed from a local environment. No exploit is available. It is suggested to upgrade the affected component.

Detailsinfo

A vulnerability, which was classified as problematic, has been found in Linux Kernel up to 7.3-rc1/7.3-rc2. Affected by this issue is the function fq_change of the file net/sched/sch_fq.c of the component fq. The manipulation of the argument TCA_FQ_QUANTUM/TCA_FQ_INITIAL_QUANTUM with an unknown input leads to a input validation vulnerability. Using CWE to declare the problem leads to CWE-20. The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly. Impacted is availability. CVE summarizes:

In the Linux kernel, the following vulnerability has been resolved: net/sched: fq: clamp quantum and initial_quantum in change path The fq change path accepts TCA_FQ_QUANTUM in [1, INT_MAX] and TCA_FQ_INITIAL_QUANTUM up to INT_MAX, while fq_init() already clamps to [1, 1<<20]. A user can override the init clamp via tc qdisc change, restoring the small-quantum deficit spin that the init clamp prevents. Narrow iq_range.max to 1<<20 so TCA_FQ_INITIAL_QUANTUM is rejected at parse time. Clamp TCA_FQ_QUANTUM to [256, 1<<20] in fq_change() and fq_init() quantum to [256, 1<<20] for tiny-MTU devices. Conditions to recreate the bug: CONFIG_NET_SCH_FQ=y. Requires CAP_NET_ADMIN (namespace-local via unshare -Urn suffices). tc qdisc add dev dummy0 root fq tc qdisc change dev dummy0 root fq quantum 1 stab data 32768 size_log 15 cell_log 0

The advisory is available at git.kernel.org. This vulnerability is handled as CVE-2026-90050 since 09/11/2026. The exploitation is known to be easy. Local access is required to approach this attack. The exploitation requires an enhanced level of successful authentication. Technical details are known, but there is no available exploit.

Upgrading to version 7.3-rc1 or 7.3-rc3 eliminates this vulnerability. Applying the patch a27498d34c3f429fb6db3aa609569f8154afa175/798283cd0fe7ba997f67e5a917f14ab40afa8d9f/72e9387884554f47b03bfd40fb8b2bf52789c68d/094cc07f98dfe70a34e2a1923af17fd29b8cf622 is able to eliminate this problem. The best possible mitigation is suggested to be upgrading to the latest version.

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Productinfo

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Version

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Website

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 4.4
VulDB Meta Temp Score: 4.2

VulDB Base Score: 4.4
VulDB Temp Score: 4.2
VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv2info

AVACAuCIA
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VectorComplexityAuthenticationConfidentialityIntegrityAvailability
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VulDB Base Score: 🔒
VulDB Temp Score: 🔒
VulDB Reliability: 🔍

Exploitinginfo

Class: Input validation
CWE: CWE-20
CAPEC: 🔒
ATT&CK: 🔒

Physical: Partially
Local: Yes
Remote: No

Availability: 🔒
Status: Not defined
Price Prediction: 🔍
Current Price Estimation: 🔒

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Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍

Countermeasuresinfo

Recommended: Upgrade
Status: 🔍

0-Day Time: 🔒

Upgrade: Kernel 7.3-rc1/7.3-rc3
Patch: a27498d34c3f429fb6db3aa609569f8154afa175/798283cd0fe7ba997f67e5a917f14ab40afa8d9f/72e9387884554f47b03bfd40fb8b2bf52789c68d/094cc07f98dfe70a34e2a1923af17fd29b8cf622

Timelineinfo

09/11/2026 CVE reserved
09/17/2026 +6 days Advisory disclosed
09/17/2026 +0 days VulDB entry created
09/17/2026 +0 days VulDB entry last update

Sourcesinfo

Vendor: kernel.org

Advisory: git.kernel.org
Status: Confirmed

CVE: CVE-2026-90050 (🔒)
GCVE (CVE): GCVE-0-2026-90050
GCVE (VulDB): GCVE-100-406550

Entryinfo

Created: 09/17/2026 18:37
Changes: 09/17/2026 18:37 (61)
Complete: 🔍
Cache ID: 216::103

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