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Fencer Vulns
high 7.5

CVE-2021-28965 json

REXML round-trip instability

published 2021-04-21 5 y ago modified 2026-09-08 2 mo ago also BIT-ruby-2021-28965 , BIT-ruby-min-2021-28965 , EUVD-2021-0797 , GHSA-8cr8-4vfw-mr7h , JLSEC-2026-1282

cvss
7.5
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
5.1%
EPSS 5.1% chance of exploitation in 30 days, percentile 92%
public exploits
0
none known

Summary

The REXML gem before 3.2.5 in Ruby before 2.6.7, 2.7.x before 2.7.3, and 3.x before 3.0.1 does not properly address XML round-trip issues. An incorrect document can be produced after parsing and serializing.

Patch / fix

  • rubygems rexml 3.2.5
  • bitnami ruby 2.6.7, 2.7.3, 3.0.1
  • bitnami ruby-min 2.6.7, 2.7.3, 3.0.1
  • ruby-lang rexml 3.2.5
  • ruby-lang ruby 2.6.7, 2.7.3, 3.0.1
  • ruby2.7 Debian 11 2.7.3-1

debian advisories DEBIAN-CVE-2021-28965

  • ruby2.3 Ubuntu 16.04 LTS 2.3.1-2~ubuntu16.04.16
  • ruby2.5 Ubuntu 18.04 LTS 2.5.1-1ubuntu1.9
  • ruby2.7 Ubuntu 20.04 LTS 2.7.0-5ubuntu1.4

ubuntu advisories UBUNTU-CVE-2021-28965

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • ruby4.0 hummingbird 1 4.0.0-33.3.hum1
  • ruby4.0-libs hummingbird 1 4.0.0-33.3.hum1
  • ruby4.0-bundled-gems hummingbird 1 4.0.0-33.3.hum1
  • ruby4.0-default-gems hummingbird 1 4.0.0-33.3.hum1
  • ruby3.3 hummingbird 1 3.3.10-23.1.hum1
  • ruby3.3-libs hummingbird 1 3.3.10-23.1.hum1
  • ruby3.3-bundled-gems hummingbird 1 3.3.10-23.1.hum1
  • ruby3.3-default-gems hummingbird 1 3.3.10-23.1.hum1

red hat advisories RHSA-2026:8838RHSA-2026:7305RHSA-2026:7307RHSA-2022:0582RHSA-2022:0581RHSA-2021:2588

  • ruby2.5 SLE Module for Basesystem 15 SP2, SLE Micro 5.0 2.5.9-4.17.1

suse advisories SUSE-SU-2021:1280-1

  • ruby4.0 openSUSE Tumbleweed 4.0.0~preview2-1.1
  • ruby3.4 openSUSE Tumbleweed 3.4.1-1.1
  • ruby2.7 openSUSE Tumbleweed 2.7.3-3.2
  • ruby3.0 openSUSE Tumbleweed 3.0.1-3.2
  • ruby3.1 openSUSE Tumbleweed 3.1.0-1.1
  • ruby3.2 openSUSE Tumbleweed 3.2.1-1.1
  • ruby3.3 openSUSE Tumbleweed 3.3.0-1.2
  • ruby2.5 openSUSE Leap 15.2 2.5.9-lp152.2.6.1

opensuse advisories openSUSE-SU-2025:15819-1openSUSE-SU-2025:14621-1openSUSE-SU-2024:11310-1openSUSE-SU-2024:11311-1openSUSE-SU-2024:11786-1openSUSE-SU-2024:12712-1

  • rubygem-pg AlmaLinux 8 1.1.4-1.module_el8.5.0+250+ba22dbf7
  • rubygem-pg AlmaLinux 8 1.1.4-1.module_el8.5.0+2623+08a8ba32
  • rubygem-abrt AlmaLinux 8 0.3.0-4.module_el8.5.0+259+8cec6917
  • rubygem-abrt AlmaLinux 8 0.3.0-4.module_el8.5.0+2623+08a8ba32
  • rubygem-bson AlmaLinux 8 4.5.0-1.module_el8.5.0+2623+08a8ba32
  • rubygem-bson AlmaLinux 8 4.5.0-1.module_el8.5.0+250+ba22dbf7
  • rubygem-mongo AlmaLinux 8 2.8.0-1.module_el8.5.0+250+ba22dbf7
  • rubygem-mongo AlmaLinux 8 2.8.0-1.module_el8.5.0+2623+08a8ba32

almalinux advisories ALSA-2021:2588ALSA-2021:2587ALSA-2021:2584

  • ruby Rocky Linux 8 2.6.7-107.module+el8.4.0+593+8d7f9f0c
  • rubygem-pg Rocky Linux 8 1.1.4-1.module+el8.5.0+738+032c9c02
  • rubygem-pg Rocky Linux 8 1.1.4-1.module+el8.4.0+446+80b53620
  • rubygem-pg Rocky Linux 8 1.1.4-1.module+el8.4.0+593+8d7f9f0c
  • rubygem-abrt Rocky Linux 8 0.3.0-4.module+el8.5.0+738+032c9c02
  • rubygem-abrt Rocky Linux 8 0.3.0-4.module+el8.3.0+167+5c390590
  • rubygem-abrt Rocky Linux 8 0.3.0-4.module+el8.4.0+592+03ff458a
  • rubygem-bson Rocky Linux 8 4.5.0-1.module+el8.4.0+593+8d7f9f0c

rocky linux advisories RLSA-2021:2588RLSA-2021:2587RLSA-2021:2584

  • ruby Alpine 3.10 2.5.9-r0
  • ruby Alpine 3.11 2.6.7-r0
  • ruby Alpine 3.24, Alpine 3.23, Alpine 3.22 +10 more 2.7.3-r0

alpine advisories ALPINE-CVE-2021-28965

Alpine secdb © Alpine Linux, from https://secdb.alpinelinux.org via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • ruby CBL-Mariner 2.0 2.7.4-1

azure linux advisories AZL-6860

Azure Linux vulnerability data, Copyright (c) Microsoft Corporation, from https://github.com/microsoft/AzureLinuxVulnerabilityData via OSV, under the MIT licence; changed: normalised to fixed package versions per release. MIT

  • ruby-rexml Arch Linux 3.2.5-1
  • ruby Arch Linux 3.0.1-1
  • gitlab Arch Linux 13.10.3-1

arch linux advisories AVG-1788AVG-1789AVG-1822

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-2021-28965 updated cvss 7.5

ruby: XML round-trip vulnerability in REXML

  • 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 Hardened Images ruby Red Hat Software Collections rh-ruby30-ruby, rh-ruby30-rubygems, rh-ruby30-ruby-libs, rh-ruby30-rubygem-irb, rh-ruby30-rubygem-rbs, rh-ruby30-rubygem-rss, +12 more
    affected: no fix available
  • Red Hat Enterprise Linux AppStream (v. 8) ruby 2.5.9-107.module+el8.4.0+10822+fe4fffb1, ruby 2.6.7-107.module+el8.4.0+10830+bbd85cce, ruby 2.7.3-136.module+el8.4.0+10728+4c884998, rubygem-pg 1.0.0-2.module+el8.1.0+3656+f80bfa1d, rubygem-pg 1.1.4-1.module+el8.1.0+3653+beb38eb0, rubygem-pg 1.2.3-1.module+el8.3.0+7192+4e3a532a, +63 more
    fixed: vendor fix RHSA-2021:2587
  • Red Hat Enterprise Linux AppStream E4S (v. 8.1) ruby 2.6.9-107.module+el8.1.0+14088+04cf326e, rubygem-pg 1.1.4-1.module+el8.1.0+3653+beb38eb0, ruby-libs 2.6.9-107.module+el8.1.0+14088+04cf326e, rubygem-abrt 0.3.0-4.module+el8.1.0+3653+beb38eb0, rubygem-bson 4.5.0-1.module+el8.1.0+3653+beb38eb0, rubygem-mongo 2.8.0-1.module+el8.1.0+3653+beb38eb0, +17 more
    fixed: vendor fix RHSA-2022:0581
  • Red Hat Enterprise Linux AppStream EUS (v. 8.2) ruby 2.6.9-107.module+el8.2.0+14086+86d863af, rubygem-pg 1.1.4-1.module+el8.1.0+3653+beb38eb0, ruby-libs 2.6.9-107.module+el8.2.0+14086+86d863af, rubygem-abrt 0.3.0-4.module+el8.1.0+3653+beb38eb0, rubygem-bson 4.5.0-1.module+el8.1.0+3653+beb38eb0, rubygem-mongo 2.8.0-1.module+el8.1.0+3653+beb38eb0, +17 more
    fixed: vendor fix RHSA-2022:0582
  • Red Hat Hardened Images ruby3.4 3.4.8-31.1.hum1, ruby4.0 4.0.0-33.3.hum1, ruby3.3 3.3.10-23.1.hum1, ruby3.4-libs 3.4.8-31.1.hum1, ruby4.0-libs 4.0.0-33.3.hum1, ruby3.3-libs 3.3.10-23.1.hum1, +6 more
    fixed: vendor fix RHSA-2026:7305
  • Red Hat Software Collections for Red Hat Enterprise Linux Server (v. 7) rh-ruby25-ruby 2.5.9-9.el7, rh-ruby26-ruby 2.6.7-119.el7, rh-ruby27-ruby 2.7.3-129.el7, rh-ruby25-ruby-irb 2.5.9-9.el7, rh-ruby25-ruby-libs 2.5.9-9.el7, rh-ruby25-rubygems 2.7.6.3-9.el7, +48 more Red Hat Software Collections for Red Hat Enterprise Linux Server EUS (v. 7.6) rh-ruby25-ruby 2.5.9-9.el7, rh-ruby25-ruby-irb 2.5.9-9.el7, rh-ruby25-ruby-libs 2.5.9-9.el7, rh-ruby25-rubygems 2.7.6.3-9.el7, rh-ruby25-rubygem-json 2.1.0-9.el7, rh-ruby25-rubygem-psych 3.0.2-9.el7, +11 more Red Hat Software Collections for Red Hat Enterprise Linux Server EUS (v. 7.7) rh-ruby25-ruby 2.5.9-9.el7, rh-ruby26-ruby 2.6.7-119.el7, rh-ruby27-ruby 2.7.3-129.el7, rh-ruby25-ruby-irb 2.5.9-9.el7, rh-ruby25-ruby-libs 2.5.9-9.el7, rh-ruby25-rubygems 2.7.6.3-9.el7, +48 more Red Hat Software Collections for Red Hat Enterprise Linux Workstation (v. 7) rh-ruby25-ruby 2.5.9-9.el7, rh-ruby26-ruby 2.6.7-119.el7, rh-ruby27-ruby 2.7.3-129.el7, rh-ruby25-ruby-irb 2.5.9-9.el7, rh-ruby25-ruby-libs 2.5.9-9.el7, rh-ruby25-rubygems 2.7.6.3-9.el7, +48 more
    fixed: vendor fix RHSA-2021:2104
  • Red Hat CloudForms Management Engine 5 ruby, ruby-irb, rubygems, ruby-libs, rubygem-rake, rubygem-rdoc, +10 more Red Hat Enterprise Linux 9 ruby, rubygems, ruby-libs, rubygem-irb, rubygem-rbs, rubygem-rss, +13 more Red Hat Hardened Images rubygem3.3-rbs 3.4.0-23.1.hum1, rubygem3.3-rss 0.3.1-23.1.hum1, rubygem3.4-rbs 3.8.0-31.1.hum1, rubygem3.4-rss 0.3.1-31.1.hum1, rubygem4.0-rss 0.3.2-33.3.hum1, rubygem3.3-irb 1.13.1-23.1.hum1, +45 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

5.06% chance of exploitation in the next 30 days, higher than 92% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
GitHub 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
NVD 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
NVD 2.0 5.0 AV:N/AC:L/Au:N/C:N/I:P/A:N
OSV 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N

Affected packages

ecosystem package affected fixed in
rubygems rexml
<3.2.5
3.2.5
bitnami ruby
<2.6.7
>=2.7.0, <2.7.3
>=3.0.0, <3.0.1
2.6.7
2.7.3
3.0.1
bitnami ruby-min
<2.6.7
>=2.7.0, <2.7.3
>=3.0.0, <3.0.1
2.6.7
2.7.3
3.0.1
julia ruby_jll
all versions
 no fix listed

Classification

Weakness
  • CWE-115 Misinterpretation of Input
  • CWE-611 Improper Restriction of XML External Entity Reference

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.