high CVSS 7.1

CVE-2021-47624·Kernel vulnerability

In the Linux kernel, the following vulnerability has been resolved: net/sunrpc: fix reference count leaks in rpc_sysfs_xprt_state_change The refcount leak issues take place in an error handling path. When the 3rd argument buf doesn't match with "offline", "online" or "remove", the function simply returns -EINVAL and forgets to decrease the reference count of a rpc_xprt object and a rpc_xprt_switch object increased by rpc_sysfs_xprt_kobj_get_xprt() and rpc_sysfs_xprt_kobj_get_xprt_switch(), causing reference count leaks of both unused objects. Fix this issue by jumping to the error handling path labelled with out_put when buf matches none of "offline", "online" or "remove".

Severity
high
Software
Kernel
Fixed in
5.16.10
Published
2024-07-16

Affected versions

From: 5.16

Until: 5.16.10

Fixed in: 5.16.10

How to fix this CVE

Update your Linux kernel to version 5.16.10 or later to patch the reference count leak in the RPC sysfs transport state change handler. This vulnerability causes memory leaks when invalid parameters are passed to the rpc_sysfs_xprt_state_change function, allowing denial of service through gradual memory exhaustion. Apply the patch immediately on systems running kernel versions 5.16 through 5.16.9.

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

Defensia detects this vulnerability

How to check if you are affected

  1. Run 'uname -r' to check your current kernel version and verify if it falls within the vulnerable range 5.16.0 to 5.16.9
  2. Check if the RPC sysfs interface is active: 'ls -la /sys/kernel/debug/sunrpc/' to confirm the sunrpc module is loaded
  3. Monitor system memory usage with 'free -h' and 'vmstat 1 10' to detect gradual memory consumption that could indicate reference count leaks
  4. Verify the patch was applied by running 'uname -r' again and confirming the kernel version is 5.16.10 or higher

FAQ

What is CVE-2021-47624?

CVE-2021-47624 is a reference count leak vulnerability in the Linux kernel's RPC sysfs transport state change handler that occurs when invalid parameters are provided, causing memory leaks and potential denial of service.

Is CVE-2021-47624 being actively exploited?

No, CVE-2021-47624 is not listed on the CISA KEV catalog and has no known public exploits, though it still poses a medium-term DoS risk through memory exhaustion.

What versions of Kernel are affected by CVE-2021-47624?

Linux kernel versions 5.16.0 through 5.16.9 are vulnerable; version 5.16.10 and later contain the fix.

How do I check if my server is vulnerable to CVE-2021-47624?

Run 'uname -r' and check if the output shows a kernel version between 5.16.0 and 5.16.9; if so, your system is vulnerable.

Does Defensia detect CVE-2021-47624?

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-2021-47624 will appear in your dashboard with remediation steps.

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References

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