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

packet: use ubuf_info completion for TX_RING packets

tpacket_snd sends skbs with frags pointing into its ring slots. Slots
are released when skb->destructor is called.

A call to skb_orphan calls skb->destructor before the skb is freed.
This can cause the slot to be reused while still linked into the skb.

Switch to standard zerocopy completion (ubuf_info) so the slot is only
released once all references to the payload are freed or copied.
Restore skb->destructor to standard sock_wfree.

The ubuf_info completion callback can be called with a NULL skb, but
only from net_zcopy_put and related API, used by zerocopy implementations
that hold their own reference on the uarg, such as MSG_ZEROCOPY. This
uarg is only ever completed from skb_zcopy_clear, so skb is always set.

To prevent userspace from aliasing in-flight state on shared ring
slots, allocate tpacket_uarg per packet, rather than per slot. This
adds a small allocation to the transmit path. Use standard kmalloc to
allow backporting to stable kernels.

The uarg holds an sk_wmem_alloc reference, rather than an sk_refcnt
reference. packet_free_tx_ring waits on sk_wmem_alloc before freeing
the ring pages. Always allocate vec->deferred for tx_ring so page-backed
rings also wait on sk_wmem_alloc when skb_copy_ubufs drops page refs
before calling tpacket_ubuf_complete.

Drop the tx_ring.pg_vec test that tpacket_destruct_skb performed before
accessing the slot. The sk_wmem_alloc reference now guarantees that the
slot is valid. The test is also not sufficient by itself, as it reads
pg_vec without pg_vec_lock, so it can race with packet_set_ring.

As a result a slot is released when its payload is copied, which can
be before transmission (e.g., in skb_orphan_frags_rx). If copied
before skb_tx_timestamp() is called, no slot timestamp is recorded,
similar to when skb_orphan() was called early in the datapath before
this patch.

Revert the now unused previous skb_zcopy_.._nouarg infra.

Depends on commit 992cc9f94ca9 ("net/packet: defer vmalloc TX_RING
free until skbs finish").
Published: 2026-10-18
Score: n/a
EPSS: n/a
KEV: No
Impact: Race condition causing premature release of TX_RING slots and potential kernel memory corruption
Action: Apply Patch
AI Analysis

Impact

The Linux kernel’s packet handling layer has a race condition where TX_RING packets are sent with skbs whose frags point into ring slots. If skb_orphan calls the skb destructor before the packet data is fully processed or copied, the slot can be released while it is still referenced by the socket buffer. This race can produce use‑after‑free corruption and prevents packet timestamps from being recorded when the packet is transmitted.

Affected Systems

All Linux kernel versions that use the legacy zero‑copy TX_RING implementation and have not incorporated commit 2a0c9afefc0ecea2cc30ccfbbbc98182a0986191 or its dependencies are affected. This includes older stable releases and any custom distributions that have not backported the change.

Risk and Exploitability

The EPSS score is not available and the vulnerability is not listed in the CISA KEV catalog. No CVSS score is provided. The flaw is a race condition that can lead to memory corruption or loss of packet timestamps. Based on the description, it is inferred that an attacker would need local access to trigger the race by invoking the zero‑copy TX_RING API, such as through a network application that uses MSG_ZEROCOPY. No public exploit has been reported, so the actual likelihood of exploitation remains uncertain, although local privilege escalation could be possible if memory corruption occurs.

Generated by OpenCVE AI on October 18, 2026 at 23:38 UTC.

Remediation

No solution or workaround provided in the CVE record.

OpenCVE Recommended Actions

  • Update the Linux kernel to a version that includes commit 2a0c9afefc0ecea2cc30ccfbbbc98182a0986191 and its downstream changes.
  • If a kernel upgrade is not immediately possible, configure the kernel to disable the zero‑copy TX_RING networking path (e.g., by disabling the MSG_ZEROCOPY feature or using a kernel configuration that turns off the affected API) until the patch is applied.
  • Until the patch is available, avoid sending packets through the zero‑copy TX_RING API and monitor for any packet timestamp anomalies that may indicate the race condition was triggered.

Generated by OpenCVE AI on October 18, 2026 at 23:38 UTC.

Tracking

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Advisories

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History

Mon, 19 Oct 2026 00:00:00 +0000

Type Values Removed Values Added
Weaknesses CWE-416
CWE-847

Sun, 18 Oct 2026 15:30:00 +0000

Type Values Removed Values Added
Description In the Linux kernel, the following vulnerability has been resolved: packet: use ubuf_info completion for TX_RING packets tpacket_snd sends skbs with frags pointing into its ring slots. Slots are released when skb->destructor is called. A call to skb_orphan calls skb->destructor before the skb is freed. This can cause the slot to be reused while still linked into the skb. Switch to standard zerocopy completion (ubuf_info) so the slot is only released once all references to the payload are freed or copied. Restore skb->destructor to standard sock_wfree. The ubuf_info completion callback can be called with a NULL skb, but only from net_zcopy_put and related API, used by zerocopy implementations that hold their own reference on the uarg, such as MSG_ZEROCOPY. This uarg is only ever completed from skb_zcopy_clear, so skb is always set. To prevent userspace from aliasing in-flight state on shared ring slots, allocate tpacket_uarg per packet, rather than per slot. This adds a small allocation to the transmit path. Use standard kmalloc to allow backporting to stable kernels. The uarg holds an sk_wmem_alloc reference, rather than an sk_refcnt reference. packet_free_tx_ring waits on sk_wmem_alloc before freeing the ring pages. Always allocate vec->deferred for tx_ring so page-backed rings also wait on sk_wmem_alloc when skb_copy_ubufs drops page refs before calling tpacket_ubuf_complete. Drop the tx_ring.pg_vec test that tpacket_destruct_skb performed before accessing the slot. The sk_wmem_alloc reference now guarantees that the slot is valid. The test is also not sufficient by itself, as it reads pg_vec without pg_vec_lock, so it can race with packet_set_ring. As a result a slot is released when its payload is copied, which can be before transmission (e.g., in skb_orphan_frags_rx). If copied before skb_tx_timestamp() is called, no slot timestamp is recorded, similar to when skb_orphan() was called early in the datapath before this patch. Revert the now unused previous skb_zcopy_.._nouarg infra. Depends on commit 992cc9f94ca9 ("net/packet: defer vmalloc TX_RING free until skbs finish").
Title packet: use ubuf_info completion for TX_RING packets
First Time appeared Linux
Linux linux Kernel
CPEs cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
Vendors & Products Linux
Linux linux Kernel
References

Subscriptions

Linux Linux Kernel
cve-icon MITRE

Status: PUBLISHED

Assigner: Linux

Published:

Updated: 2026-10-18T15:17:03.904Z

Reserved: 2026-09-25T10:25:14.353Z

Link: CVE-2026-98503

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Received

Published: 2026-10-18T16:17:01.370

Modified: 2026-10-18T16:17:01.370

Link: CVE-2026-98503

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-10-18T23:45:07Z

Weaknesses