Latest curl fails with error 55 (Failed sending HTTP request) with specific URL

[Andrew Clark]

Hi all,

I've been running a simple script that uses curl to generate a token
from a web service. Up until the last release (7.47.0-2), this had
been working fine. Now, however, I'm consistently getting

curl: (55) Failed sending HTTP request

The script I have boils down to this curl request:

$ curl --header "$header"
https://implementation.concursolutions.com/net2/oauth2/accesstoken.ashx

where $header contains

$ echo "$header"
Authorization: Basic Sm9oblNtaXRoQGRhdGFpbnRlbnNpdHlsbGMuY29tOldlbGNvbWUxCg==
X-ConsumerKey: oEcc7vFraW66kVlr3zWb6i

(these are values for a dummy account with this provider set up to
allow access to their token service)

Sending this exact request on this system

$ uname -srvo
Linux 2.6.39-400.17.1.el6uek.x86_64 #1 SMP Fri Feb 22 18:16:18 PST
2013 GNU/Linux
$ curl --version
curl 7.19.7 (x86_64-redhat-linux-gnu) libcurl/7.19.7 NSS/3.14.0.0
zlib/1.2.3 libidn/1.18 libssh2/1.4.2
Protocols: tftp ftp telnet dict ldap ldaps http file https ftps scp sftp
Features: GSS-Negotiate IDN IPv6 Largefile NTLM SSL libz

produces the desired result:

  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
139   278  139   278    0     0    311      0 --:--:-- --:--:-- --:--:--   357
<?xml version="1.0"?>
<Access_Token>
  <Instance_Url>https://implementation.concursolutions.com/</Instance_Url>
  <Token>0_/TFTaJFMhQMeLwXWie7KY1ft4=</Token>
  <Expiration_date>2/5/2017 8:32:52 PM</Expiration_date>
  <Refresh_Token>0_dTaaU2X5NKgdc9ImgbcWAYstp5pYI</Refresh_Token>
</Access_Token>

Output from cygcheck -s -v -r is attached with some information
redacted. I've also attached the output from running the above curl
command with -v.

I appreciate any insight anyone can provide on this.

Thanks,
Andrew
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