openssl with RHEL6.5 is not compatible with RHEL5.6

Issue

Hello, we are using third party certificate for authentication, they have upgraded there openssl version after heartbleeding bug

OpenSSL CVE-2014-0160 Heartbleed bug and Red Hat Enterprise Linux

and they are using RHEL 6.5, now our client is RHEL 5.6 and they have provided new certificate but RHEL 5.6 openssl version is not able to make connection with RHEL 6.5 openssl version, we are trying curl (rhel5.6)

+ curl -s -S --cacert cert.pem -u upload_us_01:********* -d oldPassword=********* -d newPassword=********* -x proxy:80 https://site
curl: (35) error:0D0C50A1:asn1 encoding routines:ASN1_item_verify:unknown message digest algorithm

certificate is generated with "Signature Algorithm: sha1WithRSAEncryption"

we tried RHEL 6.5 and it works..

can you suggest

1. is RHEL 5.6 openssl version (0.9.8e-fips-rhel5) is compatible with RHEL6.5 version ? if not what should be the workaround ?
2. is this issue with curl ? which not able to recognize new certificate signature ?