CVE-2025-21954: netmem: prevent TX of unreadable skbs

Severity: medium (CVSS 5.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.5% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2025-04-01 · updated 2026-07-30
Weakness: CWE-401

Description

In the Linux kernel, the following vulnerability has been resolved: netmem: prevent TX of unreadable skbs Currently on stable trees we have support for netmem/devmem RX but not TX. It is not safe to forward/redirect an RX unreadable netmem packet into the device's TX path, as the device may call dma-mapping APIs on dma addrs that should not be passed to it. Fix this by preventing the xmit of unreadable skbs. Tested by configuring tc redirect: sudo tc qdisc add dev eth1 ingress sudo tc filter add dev eth1 ingress protocol ip prio 1 flower ip_proto \ tcp src_ip 192.168.1.12 action mirred egress redirect dev eth1 Before, I see unreadable skbs in the driver's TX path passed to dma mapping APIs. After, I don't see unreadable skbs in the driver's TX path passed to dma mapping APIs.

Affected products

Linux kernel: from 6.12 before 6.12.20; from 6.13 before 6.13.8; 6.14-rc1, 6.14-rc2, 6.14-rc3, 6.14-rc4, 6.14-rc5, 6.14-rc6 — fixed in 6.12.20, 6.13.8

How to fix

Upgrade to a fixed version: Linux kernel 6.12.20, 6.13.8. Check the vendor advisory for mitigations.

References

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