CVE-2026-23455

critical

Published 2026-04-03 · Modified 2026-05-28

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CVSS v3

9.1

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

CVSS v4 NEW

—

not yet in upstream

VIR risk

9.1

Description

In the Linux kernel, the following vulnerability has been resolved: netfilter: nf_conntrack_h323: check for zero length in DecodeQ931() In DecodeQ931(), the UserUserIE code path reads a 16-bit length from the packet, then decrements it by 1 to skip the protocol discriminator byte before passing it to DecodeH323_UserInformation(). If the encoded length is 0, the decrement wraps to -1, which is then passed as a large value to the decoder, leading to an out-of-bounds read. Add a check to ensure len is positive after the decrement.

Predictions

Exploit likelihood

94%

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: netfilter: nf_conntrack_h323: check for zero length in DecodeQ931() 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…

Description

kernel: netfilter: nf_conntrack_h323: check for zero length in DecodeQ931()

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`	Under investigation
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 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	`5.10.253`

SUSE Affected 1 release

Version	Status	Fixed in
—	Affected	—

AlmaLinux Fixed 1 release

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

Debian Fixed 5 releases

Version	Status	Fixed in
trixie	Fixed	`6.12.85-1`
sid	Fixed	`6.19.10-1`
forky	Fixed	`6.19.10-1`
bullseye	Fixed	`6.1.170-1~deb11u1`
bookworm	Fixed	`6.1.170-1`

Red Hat Fixed 2 releases

Version	Status	Fixed in
9	Fixed	—
8	Fixed	—

References

CWEs

CWE-125

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

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