How severe is CVE-2021-28966?

CVE-2021-28966 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity high, and availability none.

Is CVE-2021-28966 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 58% (99th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-28966?

CVE-2021-28966 affects Ruby-lang Ruby. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2021-28966?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

When was CVE-2021-28966 published?

CVE-2021-28966 was published on 2021-07-30 and last updated on 2026-06-17.

CVE-2021-28966

CVE-2021-28966 is a high-severity vulnerability in Ruby-lang Ruby with a CVSS 3.x base score of 7.5. Its EPSS exploit-prediction score of 58% places it in the 99th percentile, indicating an elevated likelihood of exploitation. The underlying weakness is classified as CWE-22.

Key facts

Severity: High (CVSS 3.x base score 7.5)
CVSS v2: 5.0
EPSS exploit prediction: 58% (99th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-22
Affected product: Ruby-lang Ruby
Published: 2021-07-30
Last modified: 2026-06-17

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.

Frequently asked questions

What is CVE-2021-28966?: In Ruby through 3.0 on Windows, a remote attacker can submit a crafted path when a Web application handles a parameter with TmpDir.
How severe is CVE-2021-28966?: CVE-2021-28966 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity high, and availability none.
Is CVE-2021-28966 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 58% (99th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-28966?: CVE-2021-28966 affects Ruby-lang Ruby. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-28966?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
When was CVE-2021-28966 published?: CVE-2021-28966 was published on 2021-07-30 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:ruby-lang:ruby:*:*:*:*:*:*:*:*

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Other CWE-22 (Path Traversal) vulnerabilities

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CVE-2026-80155 — Critical (CVSS 10.0): Lantronix SLC8000 before firmware v9.7.0.5, SLC9000 before firmware v9.7.0.2, EMG8500/EMG7500 before firmware v9.7.0.1,…
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Threat intelligence

Threat-intel indicators referencing this CVE:

18.228.228.159 (ipv4-addr)
51.17.154.141 (ipv4-addr)
13.206.73.237 (ipv4-addr)