What is CVE-2017-17688?

CVE-2017-17688 is a medium-severity vulnerability in Apple Mail. CVSS score: 5.9/10. Published 2018-05-16.

How severe is CVE-2017-17688?

Medium severity. CVSS v3 base score is 5.9 out of 10.

Is CVE-2017-17688 known to be exploited?

4 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.

Vulnerability in Apple Mail

CVE-2017-17688

The OpenPGP specification allows a Cipher Feedback Mode (CFB) malleability-gadget attack that can indirectly lead to plaintext exfiltration, aka EFAIL. NOTE: third parties report that this is a problem in applications that mishandle the Modification Detection Code (MDC) feature or accept an obsolete packet type, not a problem in the OpenPGP specification

Published 2018-05-16 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 5.9 (Medium). Vector: CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N.

EPSS exploit prediction

EPSS: 0.055 (92.6th percentile), scored 2026-09-29.

Low probability of exploitation in the next 30 days, but still tracked. 93rd percentile — 92.6% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.057 · newest: 0.055 · change: -0.001

Affected products

Public proof-of-concept exploits

References

protonmail.com/blog/pgp-vulnerability-efail (Third Party Advisory, Issue Tracking)
news.ycombinator.com/item (Third Party Advisory, Issue Tracking)
www.patreon.com/posts/cybersecurity-15-18814817 (Third Party Advisory, Issue Tracking)
flaked.sockpuppet.org/2018/05/16/a-unified-timeline.html (Third Party Advisory)
www.securityfocus.com/bid/104162 (VDB Entry, Third Party Advisory, vdb-entry)
lists.gnupg.org/pipermail/gnupg-users/2018-May/060334.html (Third Party Advisory)
efail.de (Exploit, Third Party Advisory, Mitigation)
twitter.com/matthew_d_green/status/995996706457243648 (Third Party Advisory)
www.synology.com/support/security/Synology_SA_18_22 (Third Party Advisory)
www.securitytracker.com/id/1040904 (VDB Entry, Third Party Advisory, vdb-entry)

Frequently asked questions

What is CVE-2017-17688?: CVE-2017-17688 is a medium-severity vulnerability in Apple Mail. CVSS score: 5.9/10. Published 2018-05-16.
How severe is CVE-2017-17688?: Medium severity. CVSS v3 base score is 5.9 out of 10.
Is CVE-2017-17688 known to be exploited?: 4 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.