net: tap: set skb->dev before parsing virtio net header in tap_get_user_xdp()
CVE-2026-74684 · published 22 Aug 2026
How serious is it
- Severity: high, CVSS score 7.1 out of 10.
- No exploit prediction (EPSS) score yet.
- Not on the CISA list of exploited vulnerabilities.
- No public exploit in Exploit-DB.
Is your app affected by CVE-2026-74684?
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Who is affected
- Linux Linux: 924a9bc362a5223cd448ca08c3dde21235adc310 to < 61dd022c55c7307ec119e5672cb141cccbecf3b1, 924a9bc362a5223cd448ca08c3dde21235adc310 to < 15583b07fd691a844fbf7b3ad612cdc9e9a657c0, 924a9bc362a5223cd448ca08c3dde21235adc310 to < 8b444b126cd8e4473e652f529753ed4dd1360a9c, 924a9bc362a5223cd448ca08c3dde21235adc310 to < 164c31ee252ebd1ac8f44c2dfc5486b6d9a0379b
- Linux Linux: 5.12
How to check
- Find out whether you run the affected product and which version, then compare it with the versions above.
How to fix
Copies a prompt for Claude Code, Cursor or Codex that asks it to check whether you run this product.
- Apply the vendor's update or mitigation from the references below. If there is none yet, limit exposure of the affected service until there is.
- If a vulnerable version was live, check your logs and rotate the secrets that server could read.
The advisory
In the Linux kernel, the following vulnerability has been resolved:
net: tap: set skb->dev before parsing virtio net header in tap_get_user_xdp()
The commit 4f61f133f354 ("net: tap: NULL pointer derefence in
dev_parse_header_protocol when skb->dev is null") fixed a crash in
tap_get_user() by assigning skb->dev before calling tun_vnet_hdr_to_skb().
This is required because virtio_net_hdr_to_skb() may invoke
dev_parse_header_protocol(), which dereferences skb->dev. Without the
assignment, a NULL pointer dereference can occur.
However, tap_get_user_xdp() still parses the virtio-net header before
assigning skb->dev. When the vhost TX path passes an XDP buffer containing
a GSO virtio-net header but the protocol is set to zero on purpose,
tun_vnet_hdr_to_skb() can reach dev_parse_header_protocol() while skb->dev
is still NULL, resulting in a crash.
Fix this by looking up the tap device and assigning skb->dev before calling
tun_vnet_hdr_to_skb(), matching the ordering already used in
tap_get_user(). Preserve the existing RCU read-side critical section across
dev_queue_xmit().
Check your whole app
Dependencies are only half of it. Free and read-only: before you push, run npx shippable-dev scan localhost:3000 in your project folder, no account needed. For your live app, you prove it's yours with a one-line tag first.
References
- git.kernel.org/stable/c/61dd022c55c7307ec119e5672cb141cccbecf3b1
- git.kernel.org/stable/c/15583b07fd691a844fbf7b3ad612cdc9e9a657c0
- git.kernel.org/stable/c/8b444b126cd8e4473e652f529753ed4dd1360a9c
- git.kernel.org/stable/c/164c31ee252ebd1ac8f44c2dfc5486b6d9a0379b
- git.kernel.org/stable/c/3874892dd27d5387aa9a06f58d9060f18f351d24
Merged from CVE List. Last updated 25 Oct 2026. All vulnerabilities · RSS · JSON