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.
The 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.
code:
nx_secure/src/nx_secure_x509_asn1_tlv_block_parse.c
```
UINT _nx_secure_x509_asn1_tlv_block_parse(const UCHAR *buffer, ULONG *buffer_length, USHORT *tlv_type,
USHORT *tlv_tag_class, ULONG *tlv_length, const UCHAR **tlv_data, ULONG *header_length){
UINT current_index;
USHORT current_tag;
ULONG length;
ULONG length_bytes;
current_index = 0; current_tag = buffer[current_index]; /* <-- read before the bounds check */ if (*buffer_length < 1) { return(NX_SECURE_X509_ASN1_LENGTH_TOO_LONG); }```
The 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.
"}],"value":"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."}],"problemTypes":[{"descriptions":[{"cweId":"CWE-126","description":"CWE-126 Buffer Over-read","lang":"en","type":"CWE"}]}],"providerMetadata":{"dateUpdated":"2026-09-29T17:26:44.424Z","orgId":"e51fbebd-6053-4e49-959f-1b94eeb69a2c","shortName":"eclipse"},"references":[{"url":"https://github.com/eclipse-threadx/netxduo/security/advisories/GHSA-f95g-xc4w-mrcr"}],"source":{"discovery":"UNKNOWN"},"x_generator":{"engine":"Vulnogram 1.0.5"}}},"cveMetadata":{"assignerOrgId":"e51fbebd-6053-4e49-959f-1b94eeb69a2c","assignerShortName":"eclipse","cveId":"CVE-2026-102758","datePublished":"2026-09-29T17:26:44.424Z","dateReserved":"2026-09-29T16:21:58.057Z","dateUpdated":"2026-09-29T17:26:44.424Z","state":"PUBLISHED"},"dataType":"CVE_RECORD","dataVersion":"5.2"},"nvd":{"publishedDate":"2026-09-29 18:17:13","lastModifiedDate":"2026-09-29 19:00:16","problem_types":["CWE-126","CWE-126 CWE-126 Buffer Over-read"],"metrics":[],"configurations":[]},"legacy_mitre":{"record":{"CveYear":"2026","CveId":"102758","Ordinal":"1","Title":"CVE-2026-102758","CVE":"CVE-2026-102758","Year":"2026"},"notes":[{"CveYear":"2026","CveId":"102758","Ordinal":"1","NoteData":"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.","Type":"Description","Title":"CVE-2026-102758"}]}}}