CVE-2026-23456

netfilter: nf_conntrack_h323: fix OOB read in decode_int() CONS case

HIGH
8.2
CVSS Score
Published: April 3, 2026 at 03:15 PM UTC
Updated: October 19, 2026 at 07:17 PM UTC
4 products affected across 2 vendorsLinux KernelSIMATIC S7-1500 CPU 1518-4 Pn /dp MFP FirmwareSiplus S7-1500 CPU 1518-4 Pn /dp MFP Firmware

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Severity
HIGH8.2
Exploit prediction
EPSS 0.5%
SSVC
No known exploit

Description

In the Linux kernel, the following vulnerability has been resolved: netfilter: nf_conntrack_h323: fix OOB read in decode_int() CONS case In decode_int(), the CONS case calls get_bits(bs, 2) to read a length value, then calls get_uint(bs, len) without checking that len bytes remain in the buffer. The existing boundary check only validates the 2 bits for get_bits(), not the subsequent 1-4 bytes that get_uint() reads. This allows a malformed H.323/RAS packet to cause a 1-4 byte slab-out-of-bounds read. Add a boundary check for len bytes after get_bits() and before get_uint().

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

2.6.17 ≤ v < 5.10.2535.11 ≤ v < 5.15.2035.16 ≤ v < 6.1.1676.13 ≤ v < 6.18.206.19 ≤ v < 6.19.106.2 ≤ v < 6.6.1306.7 ≤ v < 6.12.785e35941d990123f155b02d5663e51a24f816b6f37.07.0 rc17.0 rc27.0 rc37.0 rc4
Vendor states this is fixed in 1e3a3593162c96e8a8de48b1e14f60c3b57fca8a (fixed)
Vendor states this is fixed in 41b417ff73a24b2c68134992cc44c88db27f482d (fixed)
Vendor states this is fixed in 52235bf88159a1ef16434ab49e47e99c8a09ab20 (fixed)
Vendor states this is fixed in 6bce72daeccca9aa1746e92d6c3d4784e71f2ebb (fixed)
Vendor states this is fixed in 774a434f8c9c8602a976b2536f65d0172a07f4d2 (fixed)
Vendor states this is fixed in a2cd54b9348e485d338b3c132338a4410c99afaf (fixed)
Vendor states this is fixed in c95dc674ebf01ecfb40388b6facfc89b81fed3b7 (fixed)
Vendor states this is fixed in fb6c3596823ec5dd09c2123340330d7448f51a59 (fixed)
Vendor states this is fixed in 2.6.17 (unaffected)
Vendor states this is fixed in 5.10.253 (unaffected)
Vendor states this is fixed in 5.15.203 (unaffected)
Vendor states this is fixed in 6.1.167 (unaffected)
Vendor states this is fixed in 6.12.78 (unaffected)
Vendor states this is fixed in 6.18.20 (unaffected)
Vendor states this is fixed in 6.19.10 (unaffected)
Vendor states this is fixed in 6.6.130 (unaffected)
Vendor states this is fixed in 7.0 (unaffected)

SSVC — Action Prioritization

SSVCNo known exploitAutomatablePartial impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

8.2HIGHLinux
Vector?

Quick Info

StatusMODIFIED
CWE
CWE-125

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