CVE-2025-21926 Affecting kernel-obs-build package, versions <6.4.0-150600.23.50.1


Severity

Recommended
0.0
medium
0
10

Based on SUSE Linux Enterprise Server security rating.

Threat Intelligence

EPSS
0.05% (16th percentile)

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  • Snyk IDSNYK-SLES156-KERNELOBSBUILD-10226203
  • published22 May 2025
  • disclosed21 May 2025

Introduced: 21 May 2025

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

How to fix?

Upgrade SLES:15.6 kernel-obs-build to version 6.4.0-150600.23.50.1 or higher.

NVD Description

Note: Versions mentioned in the description apply only to the upstream kernel-obs-build package and not the kernel-obs-build package as distributed by SLES. See How to fix? for SLES:15.6 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