Use After Free Affecting kernel-rt-devel package, versions *


Severity

Recommended
medium

Based on CentOS security rating.

Threat Intelligence

EPSS
0.02% (4th percentile)

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  • Snyk IDSNYK-CENTOS8-KERNELRTDEVEL-9620598
  • published2 Apr 2025
  • disclosed1 Apr 2025

Introduced: 1 Apr 2025

NewCVE-2025-21926  (opens in a new tab)
CWE-416  (opens in a new tab)

How to fix?

There is no fixed version for Centos:8 kernel-rt-devel.

NVD Description

Note: Versions mentioned in the description apply only to the upstream kernel-rt-devel package and not the kernel-rt-devel package as distributed by Centos. See How to fix? for Centos:8 relevant fixed versions and status.

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

net: gso: fix ownership in __udp_gso_segment

In __udp_gso_segment the skb destructor is removed before segmenting the skb but the socket reference is kept as-is. This is an issue if the original skb is later orphaned as we can hit the following bug:

kernel BUG at ./include/linux/skbuff.h:3312! (skb_orphan) RIP: 0010:ip_rcv_core+0x8b2/0xca0 Call Trace: ip_rcv+0xab/0x6e0 __netif_receive_skb_one_core+0x168/0x1b0 process_backlog+0x384/0x1100 __napi_poll.constprop.0+0xa1/0x370 net_rx_action+0x925/0xe50

The above can happen following a sequence of events when using OpenVSwitch, when an OVS_ACTION_ATTR_USERSPACE action precedes an OVS_ACTION_ATTR_OUTPUT action:

  1. OVS_ACTION_ATTR_USERSPACE is handled (in do_execute_actions): the skb goes through queue_gso_packets and then __udp_gso_segment, where its destructor is removed.
  2. The segments' data are copied and sent to userspace.
  3. OVS_ACTION_ATTR_OUTPUT is handled (in do_execute_actions) and the same original skb is sent to its path.
  4. If it later hits skb_orphan, we hit the bug.

Fix this by also removing the reference to the socket in __udp_gso_segment.

CVSS Base Scores

version 3.1