{"id":"CVE-2026-43233","summary":"netfilter: nf_conntrack_h323: fix OOB read in decode_choice()","details":"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 & 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().","modified":"2026-05-28T03:54:49.422316565Z","published":"2026-05-06T11:28:29.565Z","database_specific":{"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/43xxx/CVE-2026-43233.json","cna_assigner":"Linux"},"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/2a3aac4205e7d2f1aca2e3827de8cdd517d36c4a"},{"type":"WEB","url":"https://git.kernel.org/stable/c/35f1943d242e1b9f0b6e91c0c93bfb293a9f8224"},{"type":"WEB","url":"https://git.kernel.org/stable/c/53d32735d77ab56cc3fc7bd53a7d099418f19be1"},{"type":"WEB","url":"https://git.kernel.org/stable/c/7ef82863d42261817a6394c6c881bd6757a70f16"},{"type":"WEB","url":"https://git.kernel.org/stable/c/81f2fc5b0d0cf4696146f00f837596d10b92dead"},{"type":"WEB","url":"https://git.kernel.org/stable/c/baed0d9ba91d4f390da12d5039128ee897253d60"},{"type":"WEB","url":"https://git.kernel.org/stable/c/bcb50aa0b8f2b74a9fe5a1c7bee6f2657a288041"},{"type":"WEB","url":"https://git.kernel.org/stable/c/f0a83d0a4b7c127d32ac06d607a9214937716129"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/43xxx/CVE-2026-43233.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-43233"},{"type":"PACKAGE","url":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"ec8a8f3c31ddef0a7d9626c4b8a4baa30f3b80aa"},{"fixed":"bcb50aa0b8f2b74a9fe5a1c7bee6f2657a288041"},{"fixed":"2a3aac4205e7d2f1aca2e3827de8cdd517d36c4a"},{"fixed":"81f2fc5b0d0cf4696146f00f837596d10b92dead"},{"fixed":"7ef82863d42261817a6394c6c881bd6757a70f16"},{"fixed":"53d32735d77ab56cc3fc7bd53a7d099418f19be1"},{"fixed":"f0a83d0a4b7c127d32ac06d607a9214937716129"},{"fixed":"35f1943d242e1b9f0b6e91c0c93bfb293a9f8224"},{"fixed":"baed0d9ba91d4f390da12d5039128ee897253d60"}]}],"database_specific":{"source":"https://storage.googleapis.com/osv-test-cve-osv-conversion/osv-output/CVE-2026-43233.json"}},{"package":{"name":"Kernel","ecosystem":"Linux"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"4.15.0"},{"fixed":"5.10.252"}]},{"type":"ECOSYSTEM","events":[{"introduced":"5.11.0"},{"fixed":"5.15.202"}]},{"type":"ECOSYSTEM","events":[{"introduced":"5.16.0"},{"fixed":"6.1.165"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.2.0"},{"fixed":"6.6.128"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.7.0"},{"fixed":"6.12.75"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.13.0"},{"fixed":"6.18.16"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.19.0"},{"fixed":"6.19.6"}]}],"database_specific":{"source":"https://storage.googleapis.com/osv-test-cve-osv-conversion/osv-output/CVE-2026-43233.json"}}],"schema_version":"1.7.5","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H"}]}