Medium 5.5Published Mar 18, 2026

CVE-2026-23254net: gro: fix outer network offset

Updated under an hour ago (Oct 27, 2026, 11:00 AM ET)

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Exploited in the last 30 days

In the Linux kernel, the following vulnerability has been resolved: net: gro: fix outer network offset The udp GRO complete stage assumes that all the packets inserted the RX have the `encapsulation` flag zeroed. Such assumption is not true, as a few H/W NICs can set such flag when H/W offloading the checksum for an UDP encapsulated traffic, the tun driver can inject GSO packets with UDP encapsulation and the problematic layout can also be created via a veth based setup. Due to the above, in the problematic scenarios, udp4_gro_complete() uses the wrong network offset (inner instead of outer) to compute the outer UDP header pseudo checksum, leading to csum validation errors later on in packet processing. Address the issue always clearing the encapsulation flag at GRO completion time. Such flag will be set again as needed for encapsulated packets by udp_gro_complete().

CVSS: 5.5 MEDIUM (v3.1, NVD)CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Weakness (CWE): Not given
Known exploited: Not in CISA's KEV catalog
EPSS (exploitation in the next 30 days): Not loaded for this CVE
Assigned by: Linux
NVD analysis: Analyzed
Record last updated: May 23, 2026
First seen by InfoSec Signals: Oct 9, 2026

Affected products

Affected products

Linux Linux linux:linux (from the name)	from af276a5ac8e938c8b058e3e124073cc1e322d98b before 9d40a85138568696387ef04cd004c64612a70874; from 5ef31ea5d053a8f493a772ebad3f3ce82c35d845 before b83557bc6f560433fe5d727e241069f8db5ba709; 5ef31ea5d053a8f493a772ebad3f3ce82c35d845 builds before 2e5edb69e5d0e23ef248c56fc977039268c77a7b; 5ef31ea5d053a8f493a772ebad3f3ce82c35d845 builds before 5c2c3c38be396257a6a2e55bd601a12bb9781507; dbd9466d323a72e22efe09151253d195d36d3bf6; from 6.6.31 before 6.6.124; from 6.8.10 before 6.9	CNA record
linux linux_kernel linux:linux_kernel	from 6.6.31 before 6.6.124; from 6.8.10 before 6.9; from 6.9.1 before 6.12.70; from 6.13 before 6.18.10; 6.9; 6.9; 6.19; 6.19; and 6 more ranges	NVD

References

References

https://git.kernel.org/stable/c/9d40a85138568696387ef04cd004c64612a70874	patch
https://git.kernel.org/stable/c/b83557bc6f560433fe5d727e241069f8db5ba709	patch
https://git.kernel.org/stable/c/2e5edb69e5d0e23ef248c56fc977039268c77a7b	patch
https://git.kernel.org/stable/c/5c2c3c38be396257a6a2e55bd601a12bb9781507	patch

The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.