{"id":"CVE-2026-102758","published":"2026-09-29T18:17:13.047","lastModified":"2026-09-29T19:00:16.623","description":"The `_nx_secure_x509_asn1_tlv_block_parse()` function parses ASN.1 TLV (tag-length-value) blocks out of DER-encoded data. It is the primitive underneath all X.509 certificate parsing in NetX Secure, and therefore runs on certificates supplied by a remote peer during the TLS handshake.\n\n\n\nThe function reads the one-byte ASN.1 tag from the caller's buffer *before* checking that the buffer holds at least one byte. When a caller passes a remaining length of zero, the guard correctly returns `NX_SECURE_X509_ASN1_LENGTH_TOO_LONG`, but the read has already happened one byte past the end of the buffer.\n\n\n\ncode:\n\n\n\nnx_secure/src/nx_secure_x509_asn1_tlv_block_parse.c\n\n\n\n```\n\n\n\nUINT _nx_secure_x509_asn1_tlv_block_parse(const UCHAR *buffer, ULONG *buffer_length, USHORT *tlv_type,\n\n                                          USHORT *tlv_tag_class, ULONG *tlv_length,\n                                          const UCHAR **tlv_data, ULONG *header_length)\n\n\n{\n\n\n\nUINT   current_index;\n\n\n\nUSHORT current_tag;\n\n\n\nULONG  length;\n\n\n\nULONG  length_bytes;\n\n    current_index = 0;\n    current_tag = buffer[current_index];      /* <-- read before the bounds check */\n    if (*buffer_length < 1)\n    {\n        return(NX_SECURE_X509_ASN1_LENGTH_TOO_LONG);\n    }\n\n\n```\n\n\n\nThe remainder of the function is correctly ordered. The multi-byte length path is guarded by `length_bytes > 4 || length_bytes > *buffer_length` before its read loop, the decoded value is checked against `length > *buffer_length`, and the second single-byte length read follows its own `*buffer_length < 1` guard. The tag read is the only load placed ahead of its check.","cvssScore":null,"cvssSeverity":null,"cvssVector":null,"cwes":["CWE-126"],"vendors":[],"products":[],"references":[{"url":"https://github.com/eclipse-threadx/netxduo/security/advisories/GHSA-f95g-xc4w-mrcr","tags":[]}],"exploitRefs":[{"url":"https://github.com/eclipse-threadx/netxduo/security/advisories/GHSA-f95g-xc4w-mrcr","tags":[]}],"hasPoc":true,"ai":null}