Which products and versions are affected by CVE-2021-28966?

Affected: Ruby (Ruby-Lang); ruby-min (bitnami); ruby2.7 (debian), among others. The full list is in the CVE brief.

Is CVE-2021-28966 being exploited in the wild?

It is not listed in any known-exploited vulnerabilities catalog.

Is CVE-2021-28966 in the CISA KEV catalog?

No, it is not currently listed in the CISA Known Exploited Vulnerabilities catalog.

Is there a public exploit for CVE-2021-28966?

No public exploit code is known.

Is there a fix for CVE-2021-28966?

Fixed versions are available, including Ruby 2.5.9-r0, Ruby 2.6.7-r0, Ruby 2.6.8-r0.

How urgently should CVE-2021-28966 be patched?

Brandefense priority: patch immediately, because it is very likely to be exploited soon.

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Vulnerability Intelligence

CVE-2021-28966

High

Tempfile on Windows path traversal vulnerability

Published May 6, 2021 · Updated Sep 8, 2026 · Also known as ALPINE-CVE-2021-28966, BIT-ruby-2021-28966, BIT-ruby-min-2021-28966, GHSA-46f2-3v63-3xrp, JLSEC-2026-1283

Key Facts

Patch immediately

CVE-2021-28966 is a high-severity vulnerability (CVSS 7.5 v3.1) affecting Ruby (Ruby-Lang), ruby-min (bitnami), ruby2.7 (debian) and 2 more products.
It is not listed in any known-exploited vulnerabilities catalog. No public exploit code is known.
EPSS estimates a 58% probability of exploitation in the next 30 days.
Fixed versions are available, including Ruby 2.5.9-r0, Ruby 2.6.7-r0, Ruby 2.6.8-r0.
Brandefense priority: patch immediately, because it is very likely to be exploited soon.

CVSS v3.1

7.5

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N

EPSS (30-day exploit likelihood)

58%

Higher than 99.0% of all scored CVEs

Exploited in the wild

No known

Not in a known-exploited catalog

Public exploit code

None known

Get the full CVE-2021-28966 brief as a PDF

Every affected product and fixed release, exploitation status and a first 24 hours response checklist, emailed within minutes.

Description

In Ruby through 3.0 on Windows, a remote attacker can submit a crafted path when a Web application handles a parameter with TmpDir.

Affected Products

23 affected entries in total

Product	Affected versions	Fixed in
RubyRuby-Lang	See advisory	2.7.3
ruby-minbitnami	See advisory	2.7.3
ruby2.7debian	See advisory	0
tmpdirrubygems	See advisory	0.1.2
ruby_jlljulia	See advisory	n/a

Patched Releases

Ruby

2.5.9-r0, 2.6.7-r0, 2.6.8-r0, 2.7.3, 2.7.3-r0, 3.0.1

ruby-min

2.7.3, 3.0.1

tmpdir

0.1.2

Timeline

Publicly disclosed
May 6, 2021
Last updated
Sep 8, 2026

Weakness Type

CWE-22 Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')

References

8 more references in the full CVE brief

FAQ

Common Questions.

In Ruby through 3.0 on Windows, a remote attacker can submit a crafted path when a Web application handles a parameter with TmpDir.
Affected: Ruby (Ruby-Lang); ruby-min (bitnami); ruby2.7 (debian), among others. The full list is in the CVE brief.
It is not listed in any known-exploited vulnerabilities catalog.
No, it is not currently listed in the CISA Known Exploited Vulnerabilities catalog.
No public exploit code is known.
Fixed versions are available, including Ruby 2.5.9-r0, Ruby 2.6.7-r0, Ruby 2.6.8-r0.
Brandefense priority: patch immediately, because it is very likely to be exploited soon.

Is CVE-2021-28966 Running On Your Attack Surface?

Brandefense maps vulnerabilities like this one to your internet-facing assets and tells you exactly where to patch.