From: Denis V. Lunev <den@openvz.org> qio_channel_websock_extract_headers() returns 0 without queueing a response when the request line contains no space, unlike every sibling check which jumps to bad_request. encoutput stays empty, yet qio_channel_websock_handshake_read() still reports success and the caller arms a G_IO_OUT watch to flush nothing. Flushing that empty buffer is where QEMU crashes. Any client can trigger it before authentication on a VNC websocket port: printf 'stats\r\nx\r\n\r\n' | nc $host $port Fixes: 07e95cd529af ("io: fully parse & validate HTTP headers for websocket protocol handshake") Fixes: f69a8bde2935 ("io: send proper HTTP response for websocket errors") Fixes: CVE-2026-84788 Cc: qemu-stable@nongnu.org Cc: Daniel P. Berrangé <berrange@redhat.com> Cc: Marc-André Lureau <marcandre.lureau@redhat.com> Reviewed-by: Daniel P. Berrangé <berrange@redhat.com> Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com> Signed-off-by: Denis V. Lunev <den@openvz.org> Signed-off-by: Daniel P. Berrangé <berrange@redhat.com> --- io/channel-websock.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/io/channel-websock.c b/io/channel-websock.c index 1929abf56a..66c91ed2a2 100644 --- a/io/channel-websock.c +++ b/io/channel-websock.c @@ -230,7 +230,7 @@ qio_channel_websock_extract_headers(QIOChannelWebsock *ioc, tmp = strchr(buffer, ' '); if (!tmp) { error_setg(errp, "Missing HTTP path delimiter"); - return 0; + goto bad_request; } *tmp = '\0'; -- 2.55.0