Cyber Resilience

CVE-2026-34763

Rack ≤ 2.2.23

Published
02 April 2026
Modified
24 July 2026
Patch / advisory
View advisory
CVSS Score v3.1 5.3
Click a component to see what it means
Raw vectorCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
EPSS Score 0.0024 15th percentile
Risk Priority 43 floored blend · peak EPSS

Summary

CVE-2026-34763 is a medium-severity Permissive Regular Expression (CWE-625) vulnerability in Rack Rack. Its CVSS base score is 5.3 (Medium).

Operationally, exploitation aligns with the MITRE ATT&CK technique Exploit Public-Facing Application (T1190); ranked at the 15th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.

The strongest mitigations our analysis identified map to SI-10 (Information Input Validation) — see the control section below for these in your framework.

EU & UK References

Vulnerability Data

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 +,…

more

*, 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(s)
CWE-625

Related Threats

MITRE ATT&CK Enterprise Techniques

T1190 Exploit Public-Facing Application Initial Access
Adversaries may attempt to exploit a weakness in an Internet-facing host or system to initially access a network.
attack.mitre.org →
Derived from this CVE’s CWE(s) via the direct CWE→ATT&CK cross-walk.

CVEs Like This One

CVE-2026-34830Same product: Rack Rack
CVE-2026-34835Same product: Rack Rack
CVE-2026-32762Same product: Rack Rack
CVE-2026-22860Same product: Rack Rack
CVE-2025-27610Same product: Rack Rack
CVE-2026-26962Same product: Rack Rack
CVE-2026-26961Same product: Rack Rack
CVE-2026-34786Same product: Rack Rack
CVE-2025-27111Same product: Rack Rack
CVE-2025-25184Same product: Rack Rack

Affected Assets

rack
rack
≤ 2.2.23 · 3.0.0 — 3.1.21 · 3.2.0 — 3.2.6

Mitigating Controls

Mitigating Controls (NIST 800-53 r5) AI

SI-10 Information Input Validation partial match

SI-10 requires validity checks on inputs, directly stopping permissive regex patterns from being used for validation.

Mitigating Controls (NIST CSF 2.0) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.

PR.PS-06 mostly match
prevents

Secure SDLC practices directly require robust input-validation regex and testing that would prevent permissive patterns.

Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.

A.8.29 Security testing in development and acceptance mostly match
finds

Security testing can detect permissive regex through fuzzing or negative test cases.

A.8.25 Secure development life cycle partial match
prevents

Secure development lifecycle requires validation of input mechanisms, including regex, reducing permissive patterns.

A.8.26 Application security requirements partial match
prevents

Application security requirements mandate strict input validation rules that would catch overly permissive regex.

A.8.28 Secure coding partial match
prevents

Secure coding standards directly prohibit permissive regex and enforce strict pattern validation.

References