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CVE-2026-43233

Full vulnerability record from the local CVENow database.

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 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
HIGH
CVSS score
8.2 (v3.1)
Vulnerability status
Modified
Source identifier
416baaa9-dc9f-4396-8d5f-8c081fb06d67
Published
2026-05-06 12:16:43.417000
Last modified
2026-10-19 20:18:11.760000
View original CVE JSON 
{
  "id": "CVE-2026-43233",
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "published": "2026-05-06T12:16:43.417",
  "lastModified": "2026-10-19T20:18:11.760",
  "vulnStatus": "Modified",
  "cveTags": [],
  "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->attr & 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->cur == bs->end), the check\nnf_h323_error_boundary(bs, 0, 0) evaluates to (bs->cur + 0 > bs->end),\nwhich is false.  The subsequent get_len() call then dereferences\n*bs->cur++, 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()."
    }
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          "privilegesRequired": "NONE",
          "userInteraction": "NONE",
          "scope": "UNCHANGED",
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          "role": "CISA Coordinator",
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