CVE-2026-34763

MEDIUM

5.3

CVSS v3

Description

Rack is a modular Ruby web server interface. Prior to versions 2.2.23, 3.1.21, and 3.2.6, Rack::Directory interpolates the configured root path directly into a regular expression when deriving the displayed directory path. If root contains regex metacharacters such as +, *, or ., the prefix stripping can fail and the generated directory listing may expose the full filesystem path in the HTML output. This issue has been patched in versions 2.2.23, 3.1.21, and 3.2.6.

CWE-625

How to fix

Remediation Available

ruby-rackDebian

Fixed in:2.1.4-3+deb11u6CVE-2026-34763

Fixed in:2.2.22-0+deb12u2CVE-2026-34763

Fixed in:3.2.6-2CVE-2026-34763

librack-rubyUbuntu

Fixed in:1.5.2-3+deb8u3ubuntu1~esm11USN-8182-1

librack-ruby1.8Ubuntu

Fixed in:1.5.2-3+deb8u3ubuntu1~esm11USN-8182-1

librack-ruby1.9.1Ubuntu

Fixed in:1.5.2-3+deb8u3ubuntu1~esm11USN-8182-1

ruby-rackUbuntu

Fixed in:1.5.2-3+deb8u3ubuntu1~esm11USN-8182-1

Fixed in:1.6.4-3ubuntu0.2+esm10USN-8182-1

Fixed in:1.6.4-4ubuntu0.2+esm10USN-8182-1

Fixed in:2.0.7-2ubuntu0.1+esm10USN-8182-1

Fixed in:2.1.4-5ubuntu1.2+esm3USN-8182-1

Fixed in:2.2.7-1ubuntu0.7USN-8182-1

Fixed in:3.1.16-0.1ubuntu0.3USN-8182-1

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Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.

CVSS v3 Vector

Exploitability

Attack VectorNetwork

Attack ComplexityLow

Privileges RequiredNone

User InteractionNone

ScopeUnchanged

Impact

ConfidentialityLow

IntegrityNone

AvailabilityNone

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

Exploit Intelligence

0.24%probability of exploitation in 30 days

15thpercentile

Low risk: more likely to be exploited than 15% of all known CVEs.

References

Vendor Advisory1

github.com

Related Vulnerabilities

Other CWE-625 vulnerabilities, ordered by exploit likelihood. View all

CVE	Severity	CVSS	EPSS	Exploited	Fix
CVE-2018-8926	High	8.8	1.7%	-	Fix
CVE-2023-6544	Medium	5.4	1.1%	-	Fix
CVE-2026-23651	Critical	6.7	0.6%	-	-
CVE-2020-8910	Medium	6.5	0.5%	-	Fix
CVE-2026-32973	Critical	9.8	0.4%	-	Fix
CVE-2026-40110	High	7.3	0.3%	-	Fix

Common questions

How do I fix CVE-2026-34763?

Published advisories record a fix for 5 affected products. The "How to fix" section on this page lists the fixed version and source advisory for each one, so apply the entry matching what you actually run.

Is CVE-2026-34763 being actively exploited?

Not that we know of. CVE-2026-34763 is not in the CISA Known Exploited Vulnerabilities catalog. Its EPSS score of 0.24% is the estimated probability that it will be exploited in the next 30 days. That is higher than 15% of all scored CVEs.

How severe is CVE-2026-34763?

CVE-2026-34763 has a CVSS v3 base score of 5.3, rated medium. CVSS rates the technical impact if the vulnerability is exploited, not how likely that is, so weigh it alongside the exploit-prediction score when you decide what to patch first.

What does CVE-2026-34763 affect?

Published advisories record a fix for ruby-rack (Debian), librack-ruby (Ubuntu), librack-ruby1.8 (Ubuntu), librack-ruby1.9.1 (Ubuntu), and 1 more. Only products with a sourced advisory are listed, so treat this as what we can cite rather than a complete inventory.

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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-07-24.