File disclosure via header regex injection
Published Apr 2, 2026 · Updated Apr 2, 2026
Information disclosure in Rack before 2.2.23, 3.0.0.beta1 through 3.1.20, and 3.2.0 through 3.2.5 allows remote attackers to read unintended files. Rack::Sendfile#map_accel_path inserts the HTTP_X_ACCEL_MAPPING value into a path-matching regular expression without escaping metacharacters, letting the header rewrite X-Accel-Redirect. Exploitation requires x-accel-redirect, no application-level mapping, and an attacker-controlled header reaching Rack; nginx can then serve files from configured internal locations.
Summary
What happened
Information disclosure in Rack before 2.2.23, 3.0.0.beta1 through 3.1.20, and 3.2.0 through 3.2.5 allows remote attackers to read unintended files. Rack::Sendfile#map_accel_path inserts the HTTP_X_ACCEL_MAPPING value into a path-matching regular expression without escaping metacharacters, letting the header rewrite X-Accel-Redirect. Exploitation requires x-accel-redirect, no application-level mapping, and an attacker-controlled header reaching Rack; nginx can then serve files from configured internal locations.
The record
- CVE
- CVE-2026-34830
- Published
- Apr 2, 2026
- Updated
- Apr 2, 2026
- Vendor
- Rack
- Product
- Rack
- Classifications
- CWE-625, T1190
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Apr 2, 2026CVE publishedPublication date reported by the CVE source.
- Apr 2, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=< 2.2.23
- Affected versionversion=>= 3.0.0.beta1, < 3.1.21
- Affected versionversion=>= 3.2.0, < 3.2.6
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Weakness, pattern, technique
Public exploit references
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Technologies
Your stack
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Your stack
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