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fix: prevent pointer-wrap and oversized-length OOB reads in WebSocket parser #853

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fix: prevent pointer-wrap and oversized-length OOB reads in WebSocket parser #853

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3ef9c19
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Copilot Jul 22, 2026
6d6162f
fix: prevent pointer-wrap and oversized-length OOB in WebSocket parser
Copilot Jul 22, 2026
3fc6f84
fix: improve readability of MSB check and clarify overflow safety
Copilot Jul 22, 2026
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7 changes: 5 additions & 2 deletions http/WebSocketParser.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -12,8 +12,11 @@ static int on_frame_header(websocket_parser* parser) {
if (opcode != WS_OP_CONTINUE) {
wp->opcode = opcode;
}
int length = parser->length;
int reserve_length = MIN(length + 1, MAX_PAYLOAD_LENGTH);
size_t length = parser->length;
if (length > (size_t)MAX_PAYLOAD_LENGTH) {
return 1; // reject oversized frames; stops parsing before s_body is entered
}
size_t reserve_length = length + 1; // safe: length <= MAX_PAYLOAD_LENGTH (16M) so no overflow
Comment on lines +15 to +19
if (reserve_length > wp->message.capacity()) {
wp->message.reserve(reserve_length);
}
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8 changes: 7 additions & 1 deletion http/websocket_parser.c
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Original file line number Diff line number Diff line change
Expand Up @@ -107,6 +107,12 @@ size_t websocket_parser_execute(websocket_parser *parser, const websocket_parser
}
p--;
if(!parser->require) {
/* RFC 6455 §5.2: the most significant bit of the 64-bit payload
* length MUST be 0. Reject frames that violate this to prevent
* integer-wrap exploits on the pointer check below. */
if (parser->length > ((size_t)~(size_t)0 >> 1)) {
return GET_NPARSED();
}
Comment on lines +110 to +115
if (parser->flags & WS_HAS_MASK) {
SET_STATE(s_mask);
parser->require = 4;
Expand Down Expand Up @@ -142,7 +148,7 @@ size_t websocket_parser_execute(websocket_parser *parser, const websocket_parser
break;
case s_body:
if(parser->require) {
if(p + parser->require <= end) {
if(parser->require <= (size_t)(end - p)) {
EMIT_DATA_CB(frame_body, p, parser->require);
p += parser->require;
parser->require = 0;
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