CVE-2018-8780

CVE-2018-8780 is a critical-severity vulnerability in Ruby-lang Ruby with a CVSS 3.x base score of 9.1. Its EPSS exploit-prediction score of 10% places it in the 95th percentile, indicating an elevated likelihood of exploitation. The underlying weakness is classified as CWE-22.

Key facts

• Severity: Critical (CVSS 3.x base score 9.1)
• CVSS v2: 7.5
• EPSS exploit prediction: 10% (95th percentile)
• Actively exploited: Not listed in CISA KEV
• Weakness: CWE-22
• Affected product: Ruby-lang Ruby
• Published: 2018-04-03
• Last modified: 2026-06-17

Description

In Ruby before 2.2.10, 2.3.x before 2.3.7, 2.4.x before 2.4.4, 2.5.x before 2.5.1, and 2.6.0-preview1, the Dir.open, Dir.new, Dir.entries and Dir.empty? methods do not check NULL characters. When using the corresponding method, unintentional directory traversal may be performed.

Frequently asked questions

What is CVE-2018-8780?

In Ruby before 2.2.10, 2.3.x before 2.3.7, 2.4.x before 2.4.4, 2.5.x before 2.5.1, and 2.6.0-preview1, the Dir.open, Dir.new, Dir.entries and Dir.empty? methods do not check NULL characters. When using the corresponding method, unintentional directory traversal may be performed.

How severe is CVE-2018-8780?

CVE-2018-8780 has a CVSS 3.x base score of 9.1, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability none.

Is CVE-2018-8780 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 10% (95th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2018-8780?

CVE-2018-8780 primarily affects Ruby-lang Ruby. In total, 8 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2018-8780?

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

When was CVE-2018-8780 published?

CVE-2018-8780 was published on 2018-04-03 and last updated on 2026-06-17.

References

• http://lists.opensuse.org/opensuse-security-announce/2019-07/msg00036.html
• http://www.securityfocus.com/bid/103739
• http://www.securitytracker.com/id/1042004
• https://access.redhat.com/errata/RHSA-2018:3729
• https://access.redhat.com/errata/RHSA-2018:3730
• https://access.redhat.com/errata/RHSA-2018:3731
• https://access.redhat.com/errata/RHSA-2019:2028
• https://access.redhat.com/errata/RHSA-2020:0542
• https://access.redhat.com/errata/RHSA-2020:0591
• https://access.redhat.com/errata/RHSA-2020:0663
• https://lists.debian.org/debian-lts-announce/2018/04/msg00023.html
• https://lists.debian.org/debian-lts-announce/2018/04/msg00024.html
• https://lists.debian.org/debian-lts-announce/2018/07/msg00012.html
• https://usn.ubuntu.com/3626-1/
• https://www.debian.org/security/2018/dsa-4259
• https://www.ruby-lang.org/en/news/2018/03/28/poisoned-nul-byte-dir-cve-2018-8780/
• https://www.ruby-lang.org/en/news/2018/03/28/ruby-2-2-10-released/
• https://www.ruby-lang.org/en/news/2018/03/28/ruby-2-3-7-released/
• https://www.ruby-lang.org/en/news/2018/03/28/ruby-2-4-4-released/
• https://www.ruby-lang.org/en/news/2018/03/28/ruby-2-5-1-released/

Affected products (8)

• cpe:2.3:a:ruby-lang:ruby:*:*:*:*:*:*:*:*
• cpe:2.3:a:ruby-lang:ruby:2.6.0:preview1:*:*:*:*:*:*
• cpe:2.3:o:canonical:ubuntu_linux:14.04:*:*:*:lts:*:*:*
• cpe:2.3:o:canonical:ubuntu_linux:16.04:*:*:*:lts:*:*:*
• cpe:2.3:o:canonical:ubuntu_linux:17.10:*:*:*:*:*:*:*
• cpe:2.3:o:debian:debian_linux:7.0:*:*:*:*:*:*:*
• cpe:2.3:o:debian:debian_linux:8.0:*:*:*:*:*:*:*
• cpe:2.3:o:debian:debian_linux:9.0:*:*:*:*:*:*:*

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