UBUNTU-CVE-2025-21926
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.
02 / AFFECTED SOFTWARE
Affected packages
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03 / CONNECTIONS
Connected vulnerabilities
04 / EVIDENCE
Source records
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.
05 / REFERENCES
Further evidence
- https://git.kernel.org/linus/ee01b2f2d7d0010787c2343463965bbc283a497f
- https://ubuntu.com/security/CVE-2025-21926
- https://ubuntu.com/security/notices/USN-7510-1
- https://ubuntu.com/security/notices/USN-7510-2
- https://ubuntu.com/security/notices/USN-7510-3
- https://ubuntu.com/security/notices/USN-7510-4
- https://ubuntu.com/security/notices/USN-7510-5
- https://ubuntu.com/security/notices/USN-7510-6
- https://ubuntu.com/security/notices/USN-7510-7
- https://ubuntu.com/security/notices/USN-7510-8
- https://ubuntu.com/security/notices/USN-7511-1
- https://ubuntu.com/security/notices/USN-7511-2
- https://ubuntu.com/security/notices/USN-7511-3
- https://ubuntu.com/security/notices/USN-7512-1
- https://ubuntu.com/security/notices/USN-7516-1
- https://ubuntu.com/security/notices/USN-7516-2
- https://ubuntu.com/security/notices/USN-7516-3
- https://ubuntu.com/security/notices/USN-7516-4
- https://ubuntu.com/security/notices/USN-7516-5
- https://ubuntu.com/security/notices/USN-7516-6
- https://ubuntu.com/security/notices/USN-7516-7
- https://ubuntu.com/security/notices/USN-7516-8
- https://ubuntu.com/security/notices/USN-7516-9
- https://ubuntu.com/security/notices/USN-7517-1
- https://ubuntu.com/security/notices/USN-7517-2
- https://ubuntu.com/security/notices/USN-7517-3
- https://ubuntu.com/security/notices/USN-7518-1
- https://ubuntu.com/security/notices/USN-7539-1
- https://ubuntu.com/security/notices/USN-7540-1
- https://ubuntu.com/security/notices/USN-7593-1
- https://ubuntu.com/security/notices/USN-7602-1
- https://ubuntu.com/security/notices/USN-7605-1
- https://ubuntu.com/security/notices/USN-7605-2
- https://ubuntu.com/security/notices/USN-7606-1
- https://ubuntu.com/security/notices/USN-7628-1
- https://ubuntu.com/security/notices/USN-7640-1
- https://ubuntu.com/security/notices/USN-7764-1
- https://ubuntu.com/security/notices/USN-7764-2
- https://ubuntu.com/security/notices/USN-7765-1
- https://ubuntu.com/security/notices/USN-7766-1
- https://ubuntu.com/security/notices/USN-7767-1
- https://ubuntu.com/security/notices/USN-7767-2
- https://ubuntu.com/security/notices/USN-7779-1
- https://ubuntu.com/security/notices/USN-7790-1
- https://ubuntu.com/security/notices/USN-7800-1
- https://ubuntu.com/security/notices/USN-7801-1
- https://ubuntu.com/security/notices/USN-7801-2
- https://ubuntu.com/security/notices/USN-7801-3
- https://ubuntu.com/security/notices/USN-7802-1
- https://ubuntu.com/security/notices/USN-7809-1
- https://www.cve.org/CVERecord?id=CVE-2025-21926