SAP E-Recruiting Email Verification Bypass
Posted on 13 September 2017
SEC Consult Vulnerability Lab Security Advisory < 20170912-0 > ======================================================================= title: Email verification bypass product: SAP E-Recruiting vulnerable version: 605, 606, 616, 617 fixed version: see SAP security note number 2507798 impact: medium homepage: https://www.sap.com found: 2017-07-12 by: Marc Nimmerrichter (Office Vienna) SEC Consult Vulnerability Lab An integrated part of SEC Consult Berlin - Frankfurt/Main - Montreal - Moscow Singapore - Vienna (HQ) - Vilnius - Zurich https://www.sec-consult.com ======================================================================= Vendor description: ------------------- "SAP E-Recruiting" has recruitment and succession planning instruments that will help your company find new employees, employ them in positions that suit their capabilities, promote their professional development, and retain them in the long term. As well as enabling you to handle your companyas applicant tracking activities, "SAP E-Recruiting" ensures that you drive up-to-date human resources management, by proactively maintaining contact with applicants, potential candidates, and consequently, with your employees. Source: https://help.sap.com/saphelp_erp60_sp/helpdata/en/73/8bcf535b804808e10000000a174cb4/frameset.htm Business recommendation: ------------------------ Email address verification during the applicant registration can be bypassed. Businesses using the vulnerable component are advised to estimate the impact of insufficient email address verification on their business processes and react accordingly. It is recommended to install a patched version as soon as possible. Vulnerability overview/description: ----------------------------------- When an external applicant registers to the E-Recruiting application, he/she receives a link by email to confirm access to the provided email address. However, this measure can be bypassed and attackers can register and confirm email addresses that they do not have access to. An attacker could register email addresses not belonging to him/her. This could have a business impact, because business processes might rely on a verified email address. Furthermore, since an email address can be registered only once, an attacker could prevent other legitimate users from registering to the E-Recruiting application. Proof of concept: ----------------- The email verification link contains the "param" HTTP GET parameter with base64 encoded data. When decoded, this data contains the parameters "candidate_hrobject" and "corr_act_guid". candidate_hrobject is an incremental user ID. corr_act_guid is a random value that needs to be provided during the email verification. However, this value is not bound to the current registration, which means that the value of a previous registration can be reused. Since candidate_hrobject is incremental, it can be guessed by an attacker. An attacker who wants to register with an email address not belonging to him/her, could simply do the following: 1. Register with his own email address 2. Directly afterwards register with someone else's email address 3. Read the current value of candidate_hrobject in the confirmation link from the first registration 4. Increment this value by 1 5. Send the new value in the HTTP GET request, use the corr_act_guidparameter from the first registration 6. If this did not work: go back to step 4 to try the next ID (maybe other people registered in between the two registrations) This attack works because there is no per-registration nonce in the confirmation link. Vulnerable / tested versions: ----------------------------- The vulnerability was found in the following release of E-Recruiting (ERECRUIT): Release: 617 According to the vendor, the following versions are affected: Release: 605, 606, 616, 617 Vendor contact timeline: ------------------------ 2017-07-12: Contacted vendor via encrypted email with vulnerability description and Responsible Disclosure Policy attached at secure@sap.com 2017-07-13: Vendor confirmed the receipt of the email 2017-07-25: Vendor confirmed the vulnerability 2017-07-31: Contacted vendor to ask for patch release date and versions affected 2017-08-01: Vendor stated they are working on the fix and requested "adequate time". Link to SAP Responsible Disclosure Policy was provided. 2017-08-01: Discussing release date, requested planned patch release date and versions affected. 2017-08-02: Vendor stated that the patch cannot be published until 2017-08-31 and requested more time before advisory publication. 2017-08-23: Contacted vendor to request current patch status, planned patch release date and versions affected. 2017-08-24: Vendor stated that the patch is planned to be published on 2017-09-12. 2017-08-24: Contacted vendor to request versions affected. 2017-08-28: Vendor provided versions affected. 2017-08-29: Defined 2017-09-12 as the actual advisory publication date. 2017-08-30: Vendor confirms advisory publication date. 2017-09-07: Contacted vendor to confirm patch release date and to request number of fixed release / patch. 2017-09-07: Vendor provided security note number for the patch. 2017-09-12: Public release of advisory. Solution: --------- A patched version of SAP E-Recruiting should be installed, as the vendor has rated this vulnerability with CVSS 6.5 base score. Please refer to SAP Security Note 2507798 for further information. Workaround: ----------- None Advisory URL: ------------- https://www.sec-consult.com/en/vulnerability-lab/advisories/index.html ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ SEC Consult Vulnerability Lab SEC Consult Berlin - Frankfurt/Main - Montreal - Moscow Singapore - Vienna (HQ) - Vilnius - Zurich About SEC Consult Vulnerability Lab The SEC Consult Vulnerability Lab is an integrated part of SEC Consult. It ensures the continued knowledge gain of SEC Consult in the field of network and application security to stay ahead of the attacker. The SEC Consult Vulnerability Lab supports high-quality penetration testing and the evaluation of new offensive and defensive technologies for our customers. Hence our customers obtain the most current information about vulnerabilities and valid recommendation about the risk profile of new technologies. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Interested to work with the experts of SEC Consult? Send us your application https://www.sec-consult.com/en/career/index.html Interested in improving your cyber security with the experts of SEC Consult? Contact our local offices https://www.sec-consult.com/en/contact/index.html ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Mail: research at sec-consult dot com Web: https://www.sec-consult.com Blog: http://blog.sec-consult.com Twitter: https://twitter.com/sec_consult EOF Marc Nimmerrichter / @2017
