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Fencer Vulns
critical 9.8

CVE-2016-2338 json

An exploitable heap overflow vulnerability exists in the Psych::Emitter start_document function of Ruby.

published 2020-02-14 6 y ago modified 2026-06-17 4 mo ago also EUVD-2016-3422

cvss
9.8
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
4.7%
EPSS 4.7% chance of exploitation in 30 days, percentile 91%
public exploits
0
none known

Summary

An exploitable heap overflow vulnerability exists in the Psych::Emitter start_document function of Ruby. In Psych::Emitter start_document function heap buffer "head" allocation is made based on tags array length. Specially constructed object passed as element of tags array can increase this array size after mentioned allocation and cause heap overflow.

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2016-2338 updated cvss 9.8

ruby: heap buffer overflow in the Psych::Emitter start_document function

  • Red Hat Enterprise Linux 6 ruby, ruby-ri, ruby-irb, ruby-libs, ruby-rdoc, ruby-tcltk Red Hat Enterprise Linux 7 ruby, ruby-irb, rubygems, ruby-libs, ruby-tcltk, rubygem-json, +6 more
    affected: no fix planned “Out of support scope”
  • Red Hat Enterprise Linux 8 ruby, ruby-irb, rubygems, ruby-libs, rubygem-pg, rubygem-irb, +25 more Red Hat Enterprise Linux 9 ruby, rubygems, ruby-libs, rubygem-irb, rubygem-rbs, rubygem-rss, +13 more Red Hat Software Collections rh-ruby27-ruby, rh-ruby30-ruby, rh-ruby27-rubygems, rh-ruby30-rubygems, rh-ruby27-ruby-libs, rh-ruby30-ruby-libs, +31 more
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Exploit prediction

4.74% chance of exploitation in the next 30 days, higher than 91% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • talosintelligence.com http://www.talosintelligence.com/reports/TALOS-2016-0032/ referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
NVD 3.1 9.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Classification

Weakness

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.