CVE-2026-98503
Received Received - Intake

Linux kernel packet ring use-after-free vulnerability

Publication date: 2026-10-18

Last updated on: 2026-10-18

Assigner: kernel.org

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").

CVSS Scores

EPSS Scores

Probability:
Percentile:

Meta Information

Published
2026-10-18
Last Modified
2026-10-18
Generated
2026-10-18
AI Q&A
2026-10-18
EPSS Evaluated
N/A
NVD
CVE-2026-98503
EUVD
EUVD-2026-103743

Affected Vendors & Products

Showing 9 associated CPEs
Vendor Product Version / Range
Linux Linux 5cd8d46ea1562be80063f53c7c6a5f40224de623
Linux Linux 5cd8d46ea1562be80063f53c7c6a5f40224de623
Linux Linux 5cd8d46ea1562be80063f53c7c6a5f40224de623
Linux Linux 5cd8d46ea1562be80063f53c7c6a5f40224de623
Linux Linux 67f6fba765ef8cb19089d476e3c367212a2fbdfd
Linux Linux f2a67e68dbaeae7c88e5522873d7b908911f9f77
Linux Linux 4.14.86
Linux Linux 4.19.7
Linux Linux 4.20

Helpful Resources

Exploitability

CWE
CWE Icon
KEV
KEV Icon
CWE ID Description
CWE-UNKNOWN

Attack-Flow Graph

AI Quick Actions

Instant insights powered by AI
Executive Summary

This vulnerability in the Linux kernel involves a race condition in the packet socket implementation. When sending packets via TX_RING, the kernel previously used a destructor callback that could free ring slots prematurely while they were still linked to an skb. This allowed slots to be reused before transmission completed, potentially causing memory corruption or crashes.

Detection Guidance

This vulnerability is specific to the Linux kernel's packet socket implementation and may not have direct detection commands. Monitor for kernel crashes or unusual network behavior related to packet transmission. Check kernel logs for errors involving tpacket_snd or skb_orphan. Ensure your kernel version is updated to a patched version.

Impact Analysis

An attacker with local access could exploit this to crash the system, corrupt memory, or potentially escalate privileges. Remote exploitation is unlikely as it requires specific kernel configurations and local access to trigger the race condition.

Mitigation Strategies

Update your Linux kernel to the latest stable version that includes the fix for this vulnerability. If immediate patching is not possible, consider disabling packet socket functionality if not required. Monitor kernel security advisories for further updates.

Chat Assistant

Ask questions about this CVE
Hi! I’m here to help you understand CVE-2026-98503. Ask me anything about the vulnerability, its impact, or mitigation strategies.
0/70

EPSS Chart