CVE-2026-43233

Technical Description

In the Linux kernel, the following vulnerability has been resolved:

netfilter: nf_conntrack_h323: fix OOB read in decode_choice()

In decode_choice(), the boundary check before get_len() uses the

variable `len`, which is still 0 from its initialization at the top of

the function:

unsigned int type, ext, len = 0;

...

if (ext || (son->attr & OPEN)) {

BYTE_ALIGN(bs);

if (nf_h323_error_boundary(bs, len, 0)) /* len is 0 here */

return H323_ERROR_BOUND;

len = get_len(bs); /* OOB read */

When the bitstream is exactly consumed (bs->cur == bs->end), the check

nf_h323_error_boundary(bs, 0, 0) evaluates to (bs->cur + 0 > bs->end),

which is false. The subsequent get_len() call then dereferences

*bs->cur++, reading 1 byte past the end of the buffer. If that byte

has bit 7 set, get_len() reads a second byte as well.

This can be triggered remotely by sending a crafted Q.931 SETUP message

with a User-User Information Element

Remediation

Check the references section for vendor advisories and patches from linux. Update linux_kernel to the latest patched version. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

Affected Products

References