high CVSS 7 EPSS <0.1%

CVE-2021-47088·Kernel vulnerability

In the Linux kernel, the following vulnerability has been resolved: mm/damon/dbgfs: protect targets destructions with kdamond_lock DAMON debugfs interface iterates current monitoring targets in 'dbgfs_target_ids_read()' while holding the corresponding 'kdamond_lock'. However, it also destructs the monitoring targets in 'dbgfs_before_terminate()' without holding the lock. This can result in a use_after_free bug. This commit avoids the race by protecting the destruction with the corresponding 'kdamond_lock'.

Severity
high
Software
Kernel
Fixed in
5.15.12
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.

Read the two together. CVE-2021-47088 scores 7 on CVSS, so a successful attack would be serious — but at <0.1%, almost nobody is currently attempting it. That is a different situation from a flaw under mass exploitation, and it is usually the difference between patching on your next maintenance window and patching tonight.

Affected versions

From: 5.15

Until: 5.15.12

Fixed in: 5.15.12

How to fix this CVE

Update your Linux kernel to version 5.15.12 or later to resolve a race condition in the DAMON debugfs interface that could allow local attackers to trigger use-after-free memory corruption. Systems running kernel versions 5.15 through 5.15.11 should prioritize this update, as the vulnerability affects the monitoring target destruction mechanism when accessed concurrently with the debugfs interface.

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' and compare against the affected range (5.15.0 to 5.15.11)
  2. Step 2: Verify if DAMON debugfs interface is enabled by checking 'grep -i damon /boot/config-$(uname -r)' for CONFIG_DAMON_DBGFS=y
  3. Step 3: Search kernel logs for use-after-free errors with 'sudo dmesg | grep -i "use-after-free\|use_after_free\|UAF"' or 'sudo journalctl -k | grep -i UAF'
  4. Step 4: After patching, run 'uname -r' to confirm you're running 5.15.12 or later, then verify no UAF messages appear during normal operation over 24-48 hours

FAQ

What is CVE-2021-47088?

This vulnerability is a race condition in the Linux kernel's DAMON (Data Access Monitoring) debugfs module where concurrent access to monitoring targets can trigger a use-after-free memory bug, potentially allowing local privilege escalation.

Is CVE-2021-47088 being actively exploited?

No, this vulnerability is not listed in CISA's Known Exploited Vulnerabilities (KEV) catalog and no public exploits are available, though local attackers with system access could craft an exploit.

What versions of Kernel are affected by CVE-2021-47088?

Linux kernel versions 5.15.0 through 5.15.11 are vulnerable. The fix was integrated in kernel 5.15.12 and later versions.

How do I check if my server is vulnerable to CVE-2021-47088?

Run 'uname -r' to get your kernel version. If it shows 5.15.x where x is 11 or lower, your system is vulnerable. Additionally check 'cat /boot/config-$(uname -r) | grep DAMON_DBGFS' to confirm DAMON debugfs is compiled in.

Does Defensia detect CVE-2021-47088?

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-2021-47088 will appear in your dashboard with remediation steps and patch availability status.

Related Kernel CVEs

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References

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