medium CVSS 5.5 EPSS <0.1%

CVE-2021-47602·Kernel vulnerability

In the Linux kernel, the following vulnerability has been resolved: mac80211: track only QoS data frames for admission control For admission control, obviously all of that only works for QoS data frames, otherwise we cannot even access the QoS field in the header. Syzbot reported (see below) an uninitialized value here due to a status of a non-QoS nullfunc packet, which isn't even long enough to contain the QoS header. Fix this to only do anything for QoS data packets.

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 4% 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 this vulnerability. The issue affects QoS data frame handling in mac80211 wireless stack, where uninitialized values could be accessed in non-QoS frames that lack proper header structures. Apply the latest kernel security patches through your distribution's package manager and reboot to activate the fix.

sudo dnf check-update kernel && sudo dnf update kernel && sudo reboot

Defensia detects this vulnerability

How to check if you are affected

  1. Check installed kernel version: uname -r
  2. Verify if kernel version is between 5.11 and 5.15.10 (vulnerable range): if [[ $(uname -r | cut -d. -f1,2) == 5.11 ]] || [[ $(uname -r | cut -d. -f1,2) == 5.1[2-5] ]]; then echo 'Potentially vulnerable'; fi
  3. Search system logs for mac80211 wireless stack warnings: sudo grep -i 'mac80211\|qos\|nullfunc' /var/log/kern.log | head -20
  4. Confirm patch is applied by checking if kernel version is 5.15.11 or later: uname -r | grep -E '5\.(1[6-9]|[2-9][0-9])' && echo 'Patched' || echo 'Verify kernel version'

FAQ

What is CVE-2021-47602?

CVE-2021-47602 is a memory safety issue in the Linux kernel's mac80211 wireless driver where uninitialized values are accessed when processing non-QoS null function frames that lack proper QoS headers. This occurs because the code attempted to access QoS fields in frames that don't contain them.

Is CVE-2021-47602 being actively exploited?

No, CVE-2021-47602 is not listed on CISA's Known Exploited Vulnerabilities catalog and no public exploits are currently available. However, it was discovered through fuzzing (Syzbot), indicating it is a real kernel issue.

What versions of Kernel are affected by CVE-2021-47602?

Linux kernel versions 5.11 through 5.15.10 are vulnerable. The fix is included in kernel 5.15.11 and all subsequent releases.

How do I check if my server is vulnerable to CVE-2021-47602?

Run 'uname -r' and compare the output. If your kernel version is 5.11.x, 5.12.x, 5.13.x, 5.14.x, or 5.15.0–5.15.10, your system is vulnerable and requires a kernel update.

Does Defensia detect CVE-2021-47602?

Yes — Defensia's CVE advisory scanner compares installed package versions against the NVD database. If the Linux kernel is installed on a monitored server, CVE-2021-47602 will appear in your dashboard with remediation steps.

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References

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