GHSA-q4qf-9j86-f5mh · Severity: medium · Ecosystem: rubygems — Rack:: Static header_rules bypass via URL-encoded paths
Rack is a modular Ruby web server interface. Prior to versions 2.2.23, 3.1.21, and 3.2.6, Rack::Static#applicable_rules evaluates several header_rules types against the raw URL-encoded PATH_INFO, while the underlying file-serving path is decoded before the file is served. As a result, a request for a URL-encoded variant of a static path can serve the same file without the headers that header_rules were intended to apply. In deployments that rely on Rack::Static to attach security-relevant response headers to static content, this can allow an attacker to bypass those headers by requesting an encoded form of the path. This issue has been patched in versions 2.2.23, 3.1.21, and 3.2.6.
Conclusion & alert: CVE-2026-34786 is rated Low Risk (24.1/100): CVSS Medium severity, with low exploitation likelihood (EPSS 0.03%). Mandatory action: Monitor for updates and reassess as exploit intelligence or EPSS changes.
Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.
EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).
| # | Date | Old EPSS score | New EPSS score | Delta (New - Old) |
|---|---|---|---|---|
| 1 | 2026-04-03 | — | 0.03% | — |
Full EPSS history (1 record total)
CVSS metrics for this CVE.
| Base score | Version | Severity | Vector | Exploitability | Impact | Score source |
|---|---|---|---|---|---|---|
| 5.3 | 3.1 | MEDIUM |
|
3.9 | 1.4 | [email protected] |
GHSA-q4qf-9j86-f5mh · Severity: medium · Ecosystem: rubygems — Rack:: Static header_rules bypass via URL-encoded paths
| vendor | priority | summary | link |
|---|---|---|---|
debian
|
not yet assigned | CVE-2026-34786 not yet assigned priority: Debian including 1 source packages (ruby-rack), 5 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): open 3, resolved 2. | https://security-tracker.debian.org/tracker/CVE-2026-34786 |
redhat
|
medium | — | https://access.redhat.com/security/cve/CVE-2026-34786 |
suse
|
medium | CVE-2026-34786 severity moderate: SUSE including 2 source package names (hawk2, ruby4.0-rubygem-rack-2.2-2.2.23-1.1), 7 product×package rows across 7 product lines (SUSE Linux Enterprise High Availability Extension 12 SP5, SUSE Linux Enterprise High Availability Extension 15 SP4, … (7 product lines)): Known Not Affected 6, Fixed 1. | https://www.suse.com/security/cve/CVE-2026-34786/ |
ubuntu
|
medium | CVE-2026-34786 medium priority: Ubuntu including 1 source packages (ruby-rack), 9 status rows across 9 suites (bionic, focal, jammy, noble, questing, resolute, trusty, upstream, xenial): released 5, ignored 2, needed 1, not-affected 1. | https://ubuntu.com/security/CVE-2026-34786 |
| URL | Tags |
|---|---|
| https://github.com/rack/rack/security/advisories/GHSA-q4qf-9j86-f5mh | Vendor Advisory |