How severe is CVE-2019-16779?

CVE-2019-16779 has a CVSS score of 5.9/10, rated MEDIUM. Review your exposure and patch according to your risk tolerance.

Which packages are affected by CVE-2019-16779?

CVE-2019-16779 affects the following packages: excon (RubyGems). Ecosystems affected: RubyGems.

How do I fix CVE-2019-16779?

Update excon to 0.71.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2019-16779 is resolved across your whole dependency graph.

How do I detect CVE-2019-16779 in my RubyGems dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for excon, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2019-16779 if there is no patch (or I can't update yet)?

If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Is CVE-2019-16779 actively exploited in the wild?

No public exploit code has been indexed for CVE-2019-16779 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2019-16779?

CVE-2019-16779 has an EPSS (Exploit Prediction Scoring System) score of 1.7%, placing it in the 77th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2019-16779?

CVE-2019-16779 is classified as CWE-664 (CWE-664), CWE-362 (CWE-362). These weakness types describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2019-16779 published, and has it been updated?

CVE-2019-16779 was published on December 16, 2019 and was last updated on October 20, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

💎

💎 RubyGems

Not in CISA KEV

MEDIUM severity

CVE-2019-16779 — excon

MEDIUMFix: excon/excon@ccb57d7

CVE-2019-16779 is a medium-severity (CVSS 5.9) CWE-664 vulnerability in excon. A fix is available for excon — see the affected versions and patch details below.

In RubyGem excon, interrupted Persistent Connections May Leak Response Data

Also known asGHSA-q58g-455p-8vw9

Published

Dec 16, 2019

Updated

Oct 20, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Oct 22, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗

1.7%probability of exploitation in next 30 days

Lower Risk+0.22%

Lower risk than most CVEs77th percentile — riskier than 77% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

CVE-2019-16779 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.

Where this sits among everything scored

Of 395,249 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.

Real-World Exposure

1 pkg affected

💎excon

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects RubyGems packages — download data is not available via public APIs for these ecosystems.

Description

Impact

There was a race condition around persistent connections, where a connection which is interrupted (such as by a timeout) would leave data on the socket. Subsequent requests would then read this data, returning content from the previous response. The race condition window appears to be short, and it would be difficult to purposefully exploit this.

Patches

The problem has been patched in 0.71.0, users should upgrade to this or a newer version (if one exists).

Workarounds

Users can workaround the problem by disabling persistent connections, though this may cause performance implications.

References

See the patch for further details.

For more information

If you have any questions or comments about this advisory:

Open an issue in excon/issues
Email us at [email protected]

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
💎RubyGems	`excon`	all versions	0.71.0`bundle update excon --conservative`

Affected Products

4 products · 4 configurations

debian linuxdebian

1 version

8.0

Application

exconexcon_project

< 0.71.0

range

Application

backports sleopensuse

1 version

15.0

leapopensuse

1 version

15.1

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for excon, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update excon to 0.71.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2019-16779 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Frequently Asked Questions

### Impact There was a race condition around persistent connections, where a connection which is interrupted (such as by a timeout) would leave data on the socket. Subsequent requests would then read this data, returning content from the previous response. The race condition window appears to be short, and it would be difficult to purposefully exploit this. ### Patches The problem has been patched in 0.71.0, users should upgrade to this or a newer version (if one exists). ### Workarounds Users can workaround the problem by disabling persistent connections, though this may cause performance i