{"vuid":"VU#122919","idnumber":"122919","name":"OpenPGP and S/MIME mail client vulnerabilities","keywords":["pgp","crypto","mail"],"overview":"Mail clients may leak plaintext messages while decrypting OpenPGP and S/MIME messages.","clean_desc":"Email clients supporting the OpenPGP or S/MIME standards may be vulnerable to a CBC/CFB gadget attack which may allow an attacker to inject content into an encrypted email which would establish an exfiltration channel when decrypted by the victim's email client. For example, injecting an HTML image tag which, when rendered by the email client, sends the plaintext as part of an HTTP request. CVE-2017-17688: OpenPGP CFB Attacks\nCVE-2017-17689: S/MIME CBC Attacks Additionally some email clients, which do not isolate multiple MIME parts, allow attackers to wrap an encrypted message into plaintext MIME parts, which when decrypted and rendered by the email client results in an HTML based back-channel, eliminating the need to perform the gadget attacks. Additional details can be found in the paper describing the attacks.","impact":"A remote attack could recover plaintext from encrypted emails without access to the encryption keys.","resolution":"The CERT/CC is currently unaware of a practical solution to this problem. However, there are some mitigations that may be taken:","workarounds":"Decrypt mail outside of mail client\nUsing a separate application outside of your mail client to decrypt incoming emails prevents exfiltration channels from being opened by the email client. Disable HTML rendering\nPreventing your email client from rendering HTML will prevent the predominant form of establishing exfiltration channels. Disable Remote Content Loading\nPreventing your email client from loading remote content without permission can also help against the predominate form of establishing exfiltration channels.","sysaffected":"","thanks":"Credit is attributed to Damian Poddebniak, Christian Dresen, Jens Muller, Fabian Ising, Sebastian Schinzel1, Simon Friedberger, Juraj Somorovsky, and Jorg Schwenk","author":"This document was written by Trent Novelly.","public":["https://efail.de/","https://efail.de/efail-attack-paper.pdf","https://tools.ietf.org/html/rfc4880"],"cveids":["CVE-2017-17688 ","CVE-2017-17689"],"certadvisory":"","uscerttechnicalalert":null,"datecreated":"2018-05-09T19:23:57Z","publicdate":"2018-05-14T00:00:00Z","datefirstpublished":"2018-05-14T20:15:23Z","dateupdated":"2018-05-15T13:46:03Z","revision":23,"vrda_d1_directreport":"1","vrda_d1_population":"","vrda_d1_impact":"","cam_widelyknown":"0","cam_exploitation":"0","cam_internetinfrastructure":"0","cam_population":"0","cam_impact":"0","cam_easeofexploitation":"0","cam_attackeraccessrequired":"0","cam_scorecurrent":"0","cam_scorecurrentwidelyknown":"0","cam_scorecurrentwidelyknownexploited":"0","ipprotocol":"","cvss_accessvector":"--","cvss_accesscomplexity":"--","cvss_authentication":null,"cvss_confidentialityimpact":"--","cvss_integrityimpact":"--","cvss_availabilityimpact":"--","cvss_exploitablity":null,"cvss_remediationlevel":"ND","cvss_reportconfidence":"ND","cvss_collateraldamagepotential":"ND","cvss_targetdistribution":"ND","cvss_securityrequirementscr":"ND","cvss_securityrequirementsir":"ND","cvss_securityrequirementsar":"ND","cvss_basescore":"0","cvss_basevector":"AV:--/AC:--/Au:--/C:--/I:--/A:--","cvss_temporalscore":"0","cvss_environmentalscore":"0","cvss_environmentalvector":"CDP:ND/TD:ND/CR:ND/IR:ND/AR:ND","metric":0.0,"vulnote":null}