CVE-2026-43233 (GCVE-0-2026-43233)
Vulnerability from cvelistv5 – Published: 2026-05-06 11:28 – Updated: 2026-05-08 12:41
VLAI?
Title
netfilter: nf_conntrack_h323: fix OOB read in decode_choice()
Summary
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 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 `len`. 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().
Severity ?
8.2 (High)
Assigner
References
Impacted products
| Vendor | Product | Version | |||||||
|---|---|---|---|---|---|---|---|---|---|
| Linux | Linux |
Affected:
ec8a8f3c31ddef0a7d9626c4b8a4baa30f3b80aa , < bcb50aa0b8f2b74a9fe5a1c7bee6f2657a288041
(git)
Affected: ec8a8f3c31ddef0a7d9626c4b8a4baa30f3b80aa , < 2a3aac4205e7d2f1aca2e3827de8cdd517d36c4a (git) Affected: ec8a8f3c31ddef0a7d9626c4b8a4baa30f3b80aa , < 81f2fc5b0d0cf4696146f00f837596d10b92dead (git) Affected: ec8a8f3c31ddef0a7d9626c4b8a4baa30f3b80aa , < 7ef82863d42261817a6394c6c881bd6757a70f16 (git) Affected: ec8a8f3c31ddef0a7d9626c4b8a4baa30f3b80aa , < 53d32735d77ab56cc3fc7bd53a7d099418f19be1 (git) Affected: ec8a8f3c31ddef0a7d9626c4b8a4baa30f3b80aa , < f0a83d0a4b7c127d32ac06d607a9214937716129 (git) Affected: ec8a8f3c31ddef0a7d9626c4b8a4baa30f3b80aa , < 35f1943d242e1b9f0b6e91c0c93bfb293a9f8224 (git) Affected: ec8a8f3c31ddef0a7d9626c4b8a4baa30f3b80aa , < baed0d9ba91d4f390da12d5039128ee897253d60 (git) |
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|
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{
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"versions": [
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"version": "4.15"
},
{
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"status": "unaffected",
"version": "0",
"versionType": "semver"
},
{
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"status": "unaffected",
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},
{
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"version": "5.15.202",
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{
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{
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},
{
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"versionType": "original_commit_for_fix"
}
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}
],
"cpeApplicability": [
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],
"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnetfilter: nf_conntrack_h323: fix OOB read in decode_choice()\n\nIn decode_choice(), the boundary check before get_len() uses the\nvariable `len`, which is still 0 from its initialization at the top of\nthe function:\n\n unsigned int type, ext, len = 0;\n ...\n if (ext || (son-\u003eattr \u0026 OPEN)) {\n BYTE_ALIGN(bs);\n if (nf_h323_error_boundary(bs, len, 0)) /* len is 0 here */\n return H323_ERROR_BOUND;\n len = get_len(bs); /* OOB read */\n\nWhen the bitstream is exactly consumed (bs-\u003ecur == bs-\u003eend), the check\nnf_h323_error_boundary(bs, 0, 0) evaluates to (bs-\u003ecur + 0 \u003e bs-\u003eend),\nwhich is false. The subsequent get_len() call then dereferences\n*bs-\u003ecur++, reading 1 byte past the end of the buffer. If that byte\nhas bit 7 set, get_len() reads a second byte as well.\n\nThis can be triggered remotely by sending a crafted Q.931 SETUP message\nwith a User-User Information Element containing exactly 2 bytes of\nPER-encoded data ({0x08, 0x00}) to port 1720 through a firewall with\nthe nf_conntrack_h323 helper active. The decoder fully consumes the\nPER buffer before reaching this code path, resulting in a 1-2 byte\nheap-buffer-overflow read confirmed by AddressSanitizer.\n\nFix this by checking for 2 bytes (the maximum that get_len() may read)\ninstead of the uninitialized `len`. This matches the pattern used at\nevery other get_len() call site in the same file, where the caller\nchecks for 2 bytes of available data before calling get_len()."
}
],
"metrics": [
{
"cvssV3_1": {
"baseScore": 8.2,
"baseSeverity": "HIGH",
"vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H",
"version": "3.1"
}
}
],
"providerMetadata": {
"dateUpdated": "2026-05-08T12:41:28.161Z",
"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"shortName": "Linux"
},
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"url": "https://git.kernel.org/stable/c/bcb50aa0b8f2b74a9fe5a1c7bee6f2657a288041"
},
{
"url": "https://git.kernel.org/stable/c/2a3aac4205e7d2f1aca2e3827de8cdd517d36c4a"
},
{
"url": "https://git.kernel.org/stable/c/81f2fc5b0d0cf4696146f00f837596d10b92dead"
},
{
"url": "https://git.kernel.org/stable/c/7ef82863d42261817a6394c6c881bd6757a70f16"
},
{
"url": "https://git.kernel.org/stable/c/53d32735d77ab56cc3fc7bd53a7d099418f19be1"
},
{
"url": "https://git.kernel.org/stable/c/f0a83d0a4b7c127d32ac06d607a9214937716129"
},
{
"url": "https://git.kernel.org/stable/c/35f1943d242e1b9f0b6e91c0c93bfb293a9f8224"
},
{
"url": "https://git.kernel.org/stable/c/baed0d9ba91d4f390da12d5039128ee897253d60"
}
],
"title": "netfilter: nf_conntrack_h323: fix OOB read in decode_choice()",
"x_generator": {
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"cveMetadata": {
"assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"assignerShortName": "Linux",
"cveId": "CVE-2026-43233",
"datePublished": "2026-05-06T11:28:29.565Z",
"dateReserved": "2026-05-01T14:12:55.995Z",
"dateUpdated": "2026-05-08T12:41:28.161Z",
"state": "PUBLISHED"
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"vulnerability-lookup:meta": {
"epss": {
"cve": "CVE-2026-43233",
"date": "2026-05-09",
"epss": "0.00052",
"percentile": "0.16099"
},
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}
}
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Experimental. This forecast is provided for visualization only and may change without notice. Do not use it for operational decisions.
Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
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