What is CVE-2016-10027?

CVE-2016-10027 is a medium-severity vulnerability in Igniterealtime Smack, classified under Concurrent Execution using Shared Resource with Improper Synchronization (Race Condition). CVSS score: 5.9/10. Published 2017-01-12.

How severe is CVE-2016-10027?

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

Is CVE-2016-10027 known to be exploited?

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

Vulnerability in Igniterealtime Smack

CVE-2016-10027

Race condition in the XMPP library in Smack before 4.1.9, when the SecurityMode.required TLS setting has been set, allows man-in-the-middle attackers to bypass TLS protections and trigger use of cleartext for client authentication by stripping the "starttls" feature from a server response.

Vulnerability class: Race Condition

Published 2017-01-12 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 5.9 (Medium). Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N.

EPSS exploit prediction

EPSS: 0.015 (73.6th percentile), scored 2026-09-30.

Low probability of exploitation in the next 30 days, but still tracked. 74th percentile — 73.6% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.015 · newest: 0.015 · change: 0.000

Affected products

Igniterealtime Smack
Fedoraproject Fedora — versions 25

Weakness classification (CWE)

CWE-362 — Concurrent Execution using Shared Resource with Improper Synchronization (Race Condition)

Public proof-of-concept exploits

References

github.com/igniterealtime/Smack/commit/059ee99ba0d5ff7758829acf5a9aeede09ec820b (Patch, Third Party Advisory)
lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/… (vendor-advisory)
www.securityfocus.com/bid/95129 (VDB Entry, Third Party Advisory, vdb-entry)
issues.igniterealtime.org/projects/SMACK/issues/SMACK-739 (Issue Tracking, Vendor Advisory)
github.com/igniterealtime/Smack/commit/a9d5cd4a611f47123f9561bc5a81a4555fe7cb04 (Patch, Third Party Advisory)
www.openwall.com/lists/oss-security/2016/12/22/12 (mailing-list, Patch, Mailing List, Third Party Advisory)
community.igniterealtime.org/blogs/ignite/2016/11/22/smack-security-advisory-20… (Vendor Advisory)

Frequently asked questions

What is CVE-2016-10027?: CVE-2016-10027 is a medium-severity vulnerability in Igniterealtime Smack, classified under Concurrent Execution using Shared Resource with Improper Synchronization (Race Condition). CVSS score: 5.9/10. Published 2017-01-12.
How severe is CVE-2016-10027?: Medium severity. CVSS v3 base score is 5.9 out of 10.
Is CVE-2016-10027 known to be exploited?: 7 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.