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Linux Kernel mt7921 EUVDEUVD-2026-39852

| CVE-2026-53317 MEDIUM
2026-06-26 Linux GHSA-86cw-5chj-gj42
Denial Of Service Linux Mediatek
5.5
CVSS 3.1 · NVD
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Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata – not a confirmed exploit chain

  1. Access
    Deploy modified hostapd on mt7922 AP host
  2. Delivery
    Configure hostapd AID allocation starting at 65
  3. Exploit
    Station associates with AP and receives AID > 20
  4. Execution
    Driver passes out-of-bounds AID to mt7921/mt7922 firmware
  5. Impact
    Firmware crashes, WiFi AP service disrupted

Vulnerability Assessment

Exploitation Conditions

Exploitation requires all of the following: (1) Linux system with a Mediatek mt7921 or mt7922 WiFi chipset, (2) the interface configured in AP mode (IFTYPE_AP - client/station mode is explicitly unaffected), (3) hostapd configured to allocate station AIDs greater than 20 (specifically, the Mediatek OpenWRT-feeds-derived modified hostapd that begins allocation at AID 65 rather than 1). Stock hostapd is not vulnerable because it starts AID allocation at 1 and enforces a max-stations cap before AIDs can exceed safe limits. Limiting factors: requires local privilege to control hostapd configuration (PR:L, AV:L), non-default AP software, and specific Mediatek WiFi hardware. Remote attackers cannot independently choose their own AID in standard 802.11 operation.
Impact

Real-world risk is low despite the High availability impact in the CVSS score. All major signals converge on deprioritization: EPSS is 0.16% at the 5th percentile, there is no KEV listing, no public exploit or POC exists, and exploitation requires both specific Mediatek hardware and a non-default hostapd configuration. The CVSS vector AV:L/PR:L correctly reflects that this is a local, operator-controlled trigger - a remote attacker cannot choose their own AID in standard 802.11 since AIDs are AP-assigned. SSVC assessment: exploitation status is 'none', automatable is 'no' (requires specific local configuration), technical impact is 'partial' (DoS only, no code execution). This is a genuine medium-severity kernel stability fix rather than a prioritized security patch. The primary concern is for embedded or IoT deployments running mt7921/mt7922 in AP mode with customized hostapd from Mediatek's OpenWRT feeds.
Exploit ScenarioDerived

An operator running a Linux-based AP using mt7922 hardware deploys the Mediatek OpenWRT-derived hostapd, which allocates station AIDs starting at 65. When the 21st or any subsequent station associates with the AP, the driver passes an AID above 20 to the firmware, which crashes, taking down the WiFi interface. The AP becomes unavailable until the interface is reset or the system is rebooted. No public exploit code exists; the scenario requires physical or administrative access to deploy non-standard hostapd.
This Month Plan within 30 days. Why: MEDIUM severity (CVSS 4.0-6.9).
Patch available 0.2% exploitation probability (EPSS)

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AnalysisAIv1 – Jul 06, 2026

Firmware crash in the Linux kernel's mt76/mt7921 WiFi driver allows a local low-privileged user to cause denial of service by triggering station Association ID (AID) values above the firmware's undocumented limit of 20. Affected hardware includes Mediatek mt7922 chipsets operating in AP mode (IFTYPE_AP). Exploitation requires running a non-standard hostapd configuration that allocates AIDs starting at 65 or higher - stock hostapd is not affected. No public exploit has been identified and EPSS is 0.16% (5th percentile), indicating very low exploitation likelihood.

RemediationAI

The primary fix is to upgrade to a patched kernel: Linux 6.12.91, 6.18.33, 7.0.10, or 7.1, which add an upper bound check on station AID values in the mt7921 driver before passing them to firmware. Patch commits are linked from the kernel stable tree (https://git.kernel.org/stable/c/35835ff71e6e618155578b8e3905597edd5f601c and related). For systems that cannot immediately upgrade, the effective workaround is to replace or revert any modified hostapd binary sourced from Mediatek's OpenWRT feeds with stock hostapd, which allocates AIDs starting at 1 and keeps them below the firmware limit. Alternatively, restricting the AP's maximum associated stations to a value that keeps AID assignments below 20 via hostapd's max_num_sta parameter prevents the condition. Note that this vulnerability only manifests in AP mode - if the device operates exclusively in station mode, no mitigation is required.

Affected VersionsENISA

Linux 5c14a5f944b91371961548b1907802f74a4d2e5c <35835ff71e6e618155578b8e3905597edd5f601c
Linux patch: 7.0.10
Linux 5c14a5f944b91371961548b1907802f74a4d2e5c <4d0bf21e3e20619d51d06c0c36207aabab8b712c
Linux patch: 6.12.91
Linux patch: 6.18.33
Linux 5c14a5f944b91371961548b1907802f74a4d2e5c <6dbe70f9ef14d8ac1c24bf19fd9510978a3ab952
Linux 5.12
Linux patch: 0
Linux 5c14a5f944b91371961548b1907802f74a4d2e5c <1a4b802afe15c5b33b2dcb37a594aba2fa215d52
Linux patch: 7.1

Affected Packages

euvd linux no fix

Source: OSV (Open Source Vulnerabilities)

Affects your stack

Affects 1 package in euvd

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Technical ContextAI · show details

The mt76 driver family supports Mediatek 802.11 WiFi chipsets in the Linux kernel. The mt7921 sub-driver handles the mt7921 and mt7922 chips. When operating in IFTYPE_AP mode, the driver passes station Association IDs (AIDs) to the firmware, which appear to have an undocumented upper bound of 20. The stock hostapd daemon assigns AIDs starting at 1 and enforces its own upper bound via max_sta configuration, which prevents this condition in typical deployments. The Mediatek OpenWRT-derived modified hostapd starts AID allocation at 65, which bypasses the stock safeguard and causes the firmware to crash when it receives an AID it cannot handle. The root cause is missing bounds validation in the driver - there is no CWE assigned, but the class corresponds to improper input validation (CWE-20) or improper array index validation (CWE-129) before passing host-configured values to firmware. The CPE cpe:2.3:a:linux:linux:* confirms multiple stable kernel branches are affected, with the regression introduced at commit 5c14a5f944b91371961548b1907802f74a4d2e5c.

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Severity by source

NVD PRIMARY 5.5 MEDIUM
AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
vuln.today AI 5.5 MEDIUM

Local vector and low privilege required to control hostapd configuration; no confidentiality or integrity impact, only firmware DoS.

3.1 AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
4.0 AV:L/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
SUSE MEDIUM
Red Hat 5.5 MEDIUM

Primary rating from NVD.

CVSS VectorNVD

Attack Vector
Local
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

Lifecycle Timeline

4
CVSS changed
Jul 06, 2026 - 20:22 NVD
5.5 (MEDIUM)
Patch available
Jun 26, 2026 - 21:02 EUVD
CVE Published
Jun 26, 2026 - 19:41 nvd
MEDIUM 5.5
CVE Published
Jun 26, 2026 - 19:41 cve.org
UNKNOWN (no severity yet)

DescriptionNVD

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

wifi: mt76: mt7921: Place upper limit on station AID

Any station configured with an AID over 20 causes a firmware crash. This situation occurred in our testing using an AP interface on 7922 hardware, with a modified hostapd, sourced from Mediatek's OpenWRT feeds.

In stock hostapd, station AIDs begin counting at 1, and this configuration is prevented with an upper limit on associated stations. However, the modified hostapd began allocation at 65, which caused the firmware to crash. This fix does not allow these AIDs to work, but will prevent the firmware crash.

This crash was only seen on IFTYPE_AP interfaces, and the fix does not appear to have an effect on IFTYPE_STATION behavior.

Threat Intelligence Overview

EPSS Score
0.2%
Top 95% exploitable
Prevalence
Low
specific Mediatek mt7921/mt7922 chipset, AP-mode deployment only
Data Quality
6 sources
Confidence: High
EUVD NVD CVE.org EPSS MSRC Vendor VulDB

How this decision was reached

The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.

SignalValue
Severity MEDIUM
CISA KEV No
Public POC No
EPSS 0.2%
Patch available Yes
Active threat No
Deciding rule
MEDIUM severity (CVSS 4.0-6.9)
What every action level means
Emergency Immediate action required. Criteria: CRITICAL + in CISA KEV (actively exploited) without patch, OR CRITICAL + EPSS > 30% without patch, OR CRITICAL + active threat signals without patch.
Act Now Prioritize within 24-48h. Criteria: in KEV with patch available, OR CRITICAL + public POC, OR HIGH + EPSS > 10%, OR CRITICAL + active threat, OR any CRITICAL severity.
This Week Schedule remediation this week. Criteria: HIGH severity (CVSS 7.0-8.9). Patch within normal change window.
This Month Plan within 30 days. Criteria: MEDIUM severity (CVSS 4.0-6.9), lower exploitation probability. Include in regular patch cycle.
Monitor Track and reassess. Criteria: LOW severity (CVSS 0.1-3.9), minimal exploitation risk. No immediate action needed.

SSVC AssessmentENISA

SSVC Decision· derived
Defer
Exploitation· derived
None
System Exposure· derived
Small
Automatable· derived
No
Human Impact· derived
Medium

Priority Score

28
Low Medium High Critical
KEV: 0
EPSS: 0
CVSS: +28
PoC: 0
Weaponized: 0
Threat intel: 0
Gov advisory: 0

Attack Technique

Denial of Service MEDIUM

Denial of Service attacks render applications or systems unavailable by overwhelming resources or triggering failure conditions.

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Vendor StatusVendor

SUSE

Severity: Moderate
Product Status
SUSE Linux Enterprise Desktop 15 SP7 Affected
SUSE Linux Enterprise Desktop 15 SP7 Affected
SUSE Linux Enterprise High Availability Extension 15 SP7 Affected
SUSE Linux Enterprise High Availability Extension 15 SP7 Affected
SUSE Linux Enterprise High Availability Extension 16.0 Not-Affected

References

Advisories & patches
ADVISORY https://nvd.nist.gov/vuln/detail/CVE-2026-53317 ADVISORY https://ubuntu.com/security/notices/USN-8566-1 ADVISORY https://ubuntu.com/security/notices/USN-8568-1 ADVISORY https://vuldb.com/vuln/374359 REF https://git.kernel.org/stable/c/1a4b802afe15c5b33b2dcb37a594aba2fa215d52 REF https://git.kernel.org/stable/c/35835ff71e6e618155578b8e3905597edd5f601c REF https://git.kernel.org/stable/c/4d0bf21e3e20619d51d06c0c36207aabab8b712c REF https://git.kernel.org/stable/c/6dbe70f9ef14d8ac1c24bf19fd9510978a3ab952 REF https://git.kernel.org/stable/c/8f2ce0910b25173049910ec9a49304150534afd4 REF https://git.kernel.org/stable/c/9d63dd026644fa612a1fd348d5d3ab5d73df7fb8

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