CVE-2026-34830 — Permissive Regular Expression in Rack
Severity
5.9MEDIUMNVD
EPSS
0.0%
top 87.08%
CISA KEV
Not in KEV
Exploit
No known exploits
Affected products
1
Timeline
PublishedApr 2
Latest updateApr 17
Description
Rack is a modular Ruby web server interface. Prior to versions 2.2.23, 3.1.21, and 3.2.6, Rack::Sendfile#map_accel_path interpolates the value of the X-Accel-Mapping request header directly into a regular expression when rewriting file paths for X-Accel-Redirect. Because the header value is not escaped, an attacker who can supply X-Accel-Mapping to the backend can inject regex metacharacters and control the generated X-Accel-Redirect response header. In deployments using Rack::Sendfile with x-ac…
CVSS vector
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:NExploitability: 2.2 | Impact: 3.6
🔴Vulnerability Details
5GHSA▶
Rack::Sendfile header-based X-Accel-Mapping regex injection enables unauthorized X-Accel-Redirect↗2026-04-02
CVEList▶
Rack: Rack::Sendfile regex injection via HTTP_X_ACCEL_MAPPING header allows arbitrary file reads through nginx↗2026-04-02
OSV▶
Rack::Sendfile header-based X-Accel-Mapping regex injection enables unauthorized X-Accel-Redirect↗2026-04-02