CVE-2026-31684

medium

Published 2026-04-25 · Modified 2026-06-01

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CVSS v3

5.5

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

CVSS v4 NEW

—

not yet in upstream

VIR risk

5.5

Description

In the Linux kernel, the following vulnerability has been resolved: net: sched: act_csum: validate nested VLAN headers tcf_csum_act() walks nested VLAN headers directly from skb->data when an skb still carries in-payload VLAN tags. The current code reads vlan->h_vlan_encapsulated_proto and then pulls VLAN_HLEN bytes without first ensuring that the full VLAN header is present in the linear area. If only part of an inner VLAN header is linearized, accessing h_vlan_encapsulated_proto reads past the linear area, and the following skb_pull(VLAN_HLEN) may violate skb invariants. Fix this by requiring pskb_may_pull(skb, VLAN_HLEN) before accessing and pulling each nested VLAN header. If the header still is not fully available, drop the packet through the existing error path.

Predictions

Exploit likelihood

55%

Patch ETA

—

Heuristic predictions, AS-IS, for prioritization only.

Mitigations

Mitigation details

Source: Red Hat Errata — Red Hat Inc. · View original ↗ · Open-Errata-API

Description kernel: net: sched: act_csum: validate nested VLAN headers CVSS v3: 7.1 (CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H) Errata / fixed releases ProductPackageAdvisoryReleased Red Hat Enterprise Linux 10kernel-0:6.12.0-211.18.1.el10_2RHSA-2026:215572026-05-28T00:00:00Z Red Hat Enterprise Linux 9kernel-0:5.14.0-687.12.1.el9_8RHSA-2026:215562026-05-28T00:00:00Z Red Hat Enterprise Linux…

Description

kernel: net: sched: act_csum: validate nested VLAN headers

CVSS v3: 7.1 (CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H)

Errata / fixed releases

Product	Package	Advisory	Released
Red Hat Enterprise Linux 10	`kernel-0:6.12.0-211.18.1.el10_2`	RHSA-2026:21557	2026-05-28T00:00:00Z
Red Hat Enterprise Linux 9	`kernel-0:5.14.0-687.12.1.el9_8`	RHSA-2026:21556	2026-05-28T00:00:00Z
Red Hat Enterprise Linux 9	`kernel-0:5.14.0-687.12.1.el9_8`	RHSA-2026:21556	2026-05-28T00:00:00Z

Package state

Product	Package	State
Red Hat Enterprise Linux 6	`kernel`	Not affected
Red Hat Enterprise Linux 7	`kernel`	Affected
Red Hat Enterprise Linux 7	`kernel-rt`	Affected
Red Hat Enterprise Linux 8	`kernel`	Affected
Red Hat Enterprise Linux 8	`kernel-rt`	Affected
Red Hat Enterprise Linux 9	`kernel-rt`	Affected

Apply commands

bash fix

Apply RHSA-2026:21557 for Red Hat Enterprise Linux 10

yum update -y kernel
# or:
dnf upgrade -y kernel

Affected

Vendor	Product	Version
redhat	Red Hat Enterprise Linux 6	`Not affected`
redhat	Red Hat Enterprise Linux 7	`Affected`
redhat	Red Hat Enterprise Linux 7	`Affected`
redhat	Red Hat Enterprise Linux 8	`Affected`
redhat	Red Hat Enterprise Linux 8	`Affected`
redhat	Red Hat Enterprise Linux 9	`Affected`

OS impact

Linux kernel Affected 2 releases

Version	Status	Fixed in
7.0	Affected	—
—	Affected	`4.20`

SUSE Affected 1 release

Version	Status	Fixed in
—	Affected	—

Debian Mixed 5 releases

Version	Status	Fixed in
trixie	Fixed	`6.12.85-1`
sid	Fixed	`6.19.14-1`
forky	Fixed	`6.19.14-1`
bullseye	Affected	—
bookworm	Affected	—

AlmaLinux Fixed 1 release

Version	Status	Fixed in
8	Fixed	`kernel-doc-4.18.0-553.126.1.el8_10.noarch.rpm`

Red Hat Fixed 2 releases

Version	Status	Fixed in
9	Fixed	—
8	Fixed	—

References

Community-verified mitigations for this CVE will appear above when contributors publish them.

Verify integrity in audit chain (admin only). AS-IS.