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Vulnerabilities

Vulnerability · CVE-2026-43233

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 chec…

Published May 6, 2026 · catalog updated Jun 17, 2026 · linux kernel

Check if you run it

No confirmed exploitation is on record for CVE-2026-43233. EPSS is 0.46%. Act only if a listed version of linux kernel is installed.

Gaps on this record

  • No vendor fix or required action is stored. Compare the linked advisory before you change production.
Severity
High8.2
Known exploitation
Not in CISA/VulnCheck KEV
EPSS
0.46%
Remediation
Advisory link
Affected products
cpe linux/linux kernel

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 , 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 containing exactly 2 bytes of PER-encoded data ({0x08, 0x00}) to port 1720 through a firewall with the nf_conntrack_h323 helper active. The decoder fully consumes the PER buffer before reaching this code path, resulting in a 1-2 byte heap-buffer-overflow read confirmed by AddressSanitizer. Fix this by checking for 2 bytes (the maximum that get_len() may read) instead of the uninitialized . This matches the pattern used at every other get_len() call site in the same file, where the caller checks for 2 bytes of available data before calling get_len().

Are you affected?

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  • cpe linux/linux kernel4.15

How to fix CVE-2026-43233

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

No confirmed exploitation is on record for CVE-2026-43233. EPSS is 0.46%. Act only if a listed version of linux kernel is installed.

Which versions are affected?

Compare what you have installed with linux/linux kernel 4.15. Compare the installed version with the linked vendor advisory before you change production.

What should an analyst verify?

CWE-125: Out-of-bounds Read. EPSS 0.46%. There is no CISA KEV listing. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.

Code

The project this record applies to. Exploit listings stay in References.

Timeline

Detection, updates, and resolution for this record.

  1. May 6, 2026 · NIST NVD

    Detected

    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 , 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))

  2. Jun 17, 2026 · NIST NVD

    Updated

    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 , 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))

Sources

  • CVE.orgVulnerability recordCVE-2026-43233

    Official CVE identifier

    cve.org
  • FIRST EPSSExploitation probabilityCVE-2026-43233

    30-day exploitation probability 0.5%

    first.org
  • NIST NVDVulnerability recordCVE-2026-43233

    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 , which is still 0 from its initialization at the top of the function

    nvd.nist.gov

References

Freshness

Last verified in this catalog Oct 18, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.