CVE-2025-21921 Affecting kernel-uek-modules-extra-netfilter package, versions <0:6.12.0-101.33.4.3.el9uek


Severity

Recommended
high

Based on Oracle Linux security rating.

Threat Intelligence

EPSS
0.03% (6th percentile)

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  • Snyk IDSNYK-ORACLE9-KERNELUEKMODULESEXTRANETFILTER-10789850
  • published19 Jul 2025
  • disclosed1 Apr 2025

Introduced: 1 Apr 2025

CVE-2025-21921  (opens in a new tab)

How to fix?

Upgrade Oracle:9 kernel-uek-modules-extra-netfilter to version 0:6.12.0-101.33.4.3.el9uek or higher.
This issue was patched in ELSA-2025-20480.

NVD Description

Note: Versions mentioned in the description apply only to the upstream kernel-uek-modules-extra-netfilter package and not the kernel-uek-modules-extra-netfilter package as distributed by Oracle. See How to fix? for Oracle:9 relevant fixed versions and status.

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

net: ethtool: netlink: Allow NULL nlattrs when getting a phy_device

ethnl_req_get_phydev() is used to lookup a phy_device, in the case an ethtool netlink command targets a specific phydev within a netdev's topology.

It takes as a parameter a const struct nlattr *header that's used for error handling :

   if (!phydev) {
           NL_SET_ERR_MSG_ATTR(extack, header,
                               &#34;no phy matching phyindex&#34;);
           return ERR_PTR(-ENODEV);
   }

In the notify path after a ->set operation however, there's no request attributes available.

The typical callsite for the above function looks like:

phydev = ethnl_req_get_phydev(req_base, tb[ETHTOOL_A_XXX_HEADER],
                  info-&gt;extack);

So, when tb is NULL (such as in the ethnl notify path), we have a nice crash.

It turns out that there's only the PLCA command that is in that case, as the other phydev-specific commands don't have a notification.

This commit fixes the crash by passing the cmd index and the nlattr array separately, allowing NULL-checking it directly inside the helper.

CVSS Base Scores

version 3.1