<p dir="auto">e.g. <a href="http://t_rost.rosfirm.ru/" rel="nofollow">http://t_rost.rosfirm.ru/</a> is valid URL</p>
<p dir="auto"><a href="https://github.com/symfony/Validator/blob/0a118a6e885937378d41b97b152ecec2058c89dc/Constraints/UrlValidator.php#L29">https://github.com/symfony/Validator/blob/0a118a6e885937378d41b97b152ecec2058c89dc/Constraints/UrlValidator.php#L29</a></p>
<p dir="auto">Url validator accept as valid an url like the following:<br>
<a href="http://testsub+domanin.domanin.com:8080/test" rel="nofollow">http://testsub+domanin.domanin.com:8080/test</a></p>
<p dir="auto">but does not accept<br>
<a href="http://test_sub_domanin.domanin.com:8080/test" rel="nofollow">http://test_sub_domanin.domanin.com:8080/test</a></p>
<p dir="auto">The problem seems to be here:<br>
symfony / src / Symfony / Component / Validator / Constraints / UrlValidator.php<br>
Line 28:                ([\pL\pN\pS-]+.)+[\pL]+                   # a domain name</p>
<p dir="auto">The fix can be as simple as replacing \pS (mathematical symbol) with \pP (punctuation character) or even better i think \pPc (Connector Punctuation character)</p>