medium CVSS 5.5 EPSS <0.1%

CVE-2021-47583·Kernel vulnerability

In the Linux kernel, the following vulnerability has been resolved: media: mxl111sf: change mutex_init() location Syzbot reported, that mxl111sf_ctrl_msg() uses uninitialized mutex. The problem was in wrong mutex_init() location. Previous mutex_init(&state->msg_lock) call was in ->init() function, but dvb_usbv2_init() has this order of calls: dvb_usbv2_init() dvb_usbv2_adapter_init() dvb_usbv2_adapter_frontend_init() props->frontend_attach() props->init() Since mxl111sf_* devices call mxl111sf_ctrl_msg() in ->frontend_attach() internally we need to initialize state->msg_lock before frontend_attach(). To achieve it, ->probe() call added to all mxl111sf_* devices, which will simply initiaize mutex.

Severity
medium
Software
Kernel
Fixed in
5.15.11
Published

How likely is exploitation

FIRST's Exploit Prediction Scoring System puts the probability of this CVE being exploited in the next 30 days at <0.1% — higher than 5% of all published CVEs. EPSS is an independent forecast of exploitation, not a severity rating: it says nothing about how much damage a successful attack does, which is what a CVSS score measures.

Affected versions

From: 5.11

Until: 5.15.11

Fixed in: 5.15.11

How to fix this CVE

Update your Linux kernel to version 5.15.11 or later to resolve a race condition in the MXL111SF media driver where the message lock mutex was initialized after being used during device initialization. This timing issue could lead to kernel crashes or hangs when MXL111SF-based DVB-USB devices are attached. Systems running kernel versions 5.11 through 5.15.10 should prioritize this update.

sudo dnf update kernel kernel-devel

Defensia detects this vulnerability

How to check if you are affected

  1. Step 1: Check your current kernel version with: uname -r (ensure it is 5.15.11 or later)
  2. Step 2: Verify if MXL111SF media driver is loaded with: lsmod | grep mxl111sf
  3. Step 3: Check system logs for mutex-related errors: sudo journalctl -b | grep -i 'mutex\|mxl111sf'
  4. Step 4: After kernel update, reboot and confirm new version: uname -r (should show 5.15.11+)

FAQ

What is CVE-2021-47583?

This vulnerability involves an uninitialized mutex in the MXL111SF media driver due to incorrect initialization ordering during device probe. The mutex is used in frontend attachment before it is properly initialized, potentially causing kernel crashes or deadlocks.

Is CVE-2021-47583 being actively exploited?

No, this vulnerability is not listed in the CISA Known Exploited Vulnerabilities (KEV) catalog and has no public exploit availability. It requires direct kernel access and is primarily a local denial-of-service risk.

What versions of Kernel are affected by CVE-2021-47583?

Linux kernel versions 5.11 through 5.15.10 are vulnerable. The fix was merged in kernel 5.15.11 and stable releases thereafter.

How do I check if my server is vulnerable to CVE-2021-47583?

Run uname -r and verify your kernel version is 5.15.10 or earlier; if so, your system is vulnerable. Also check if the mxl111sf driver is present with lsmod | grep mxl111sf.

Does Defensia detect CVE-2021-47583?

Yes — Defensia's CVE advisory scanner compares installed package versions against the NVD database. If Kernel is installed on a monitored server, CVE-2021-47583 will appear in your dashboard with remediation steps.

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References

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