CVE-2026-23456: netfilter: nf_conntrack_h323: fix OOB read in decode_int() CONS case
In the Linux kernel, the following vulnerability has been resolved:
netfilter: nfconntrackh323: fix OOB read in decodeint() CONS case
In decodeint(), the CONS case calls getbits(bs, 2) to read a length value, then calls getuint(bs, len) without checking that len bytes remain in the buffer. The existing boundary check only validates the 2 bits for getbits(), not the subsequent 1-4 bytes that getuint() 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 getbits() and before getuint().
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
debian/linuxto a version that resolves this vulnerability.Fixed in 6.1.176-1Fixed in 6.1.190-1Fixed in 6.12.107-1Fixed in 6.12.113-1Fixed in 7.2.12-1Fixed in 7.2.13-1 - Compensating control
In netfilter nf_conntrack_h323 decode_int()'s CONS case, add a boundary check that verifies len bytes remain in the buffer after get_bits(bs, 2) and before calling get_uint(bs, len).
Event History
Frequently Asked Questions
Which systems are realistically exposed?
Linux kernel systems that process H.323/RAS traffic through the nf_conntrack_h323 component are exposed to malformed packets that reach this parsing path. The vulnerability is network-reachable and does not require attacker privileges or user interaction.
What can a successful exploit affect?
The flaw allows a malformed packet to trigger a slab out-of-bounds read of 1 to 4 bytes. The supplied severity vector indicates high availability impact and low confidentiality impact, with no integrity impact.