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Header lines with improper terminators manipulated by Burp in strange ways

David Oct 29, 2017 12:54AM UTC

I'm currently testing an embedded device with a cgi-script that terminates header lines with only '\n', and '\n\n' at the end of all headers. While not RFC-compliant, browsers seem to handle this just fine. However, when it goes through Burp, the '\n\n' is replaced with '\n\r\n\r\n', which the browser interprets as *3* newlines, causing an extra newline to appear in the browser, breaking the parsing of the responses to XHRs.

Tested on 1.7.27 free, can test on pro at work next week.


Paul Johnston Oct 31, 2017 02:34PM UTC Support Center agent

Hi David,

Thanks for reporting this. I’ve had a look and can reproduce the issue. This is a bug in Burp and we will endeavor to fix this. In the meantime, this extension should provide a workaround:

- https://gist.github.com/pajswigger/1f595793390e0badace669c4b7f7fc98

Please let us know if you need any further assistance.


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