Vulnerability in Rack
CVSS score
6.5
EPSS probability
%0.2
Risk score
0.0
Published
6 mo ago
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Vulnerability description
DayBreach CVE AI Research
CVE-2026-34831 has vendor, distribution, patch and security-source records on file. We can compare them and prepare an explanation linked to the evidence.
Rack is a modular Ruby web server interface. Prior to versions 2.2.23, 3.1.21, and 3.2.6, Rack::Files#fail sets the Content-Length response header using String#size instead of String#bytesize. When the response body contains multibyte UTF-8 characters, the declared Content-Length is smaller than the number of bytes actually sent on the wire. Because Rack::Files reflects the requested path in 404 responses, an attacker can trigger this mismatch by requesting a non-existent path containing percent-encoded UTF-8 characters. This results in incorrect HTTP response framing and may cause response desynchronization in deployments that rely on the incorrect Content-Length value. This issue has been patched in versions 2.2.23, 3.1.21, and 3.2.6.
IMPACT: Affected Products and Software
RED HAT CSAF/VEX: Product Impact Check
SCORING: CVSS from Multiple Sources
CVSS Scores
The Common Vulnerability Scoring System is a standardised framework for assessing the severity of vulnerabilities in software and systems. We collect and display CVSS scores from several sources for each CVE.
| SCORE | VERSION | SEVERITY | VECTOR | SOURCE |
|---|---|---|---|---|
| 6.5 | CVSS V31 | MEDIUM | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N | NVD |
| 4.8 | CVSS V31 | MEDIUM | CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N | NVD |
Patch and Remediation Guide
Solution & Remediation Advisory
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Public exploit and active exploitation status
Verified exploit intelligence
No verified public PoC, exploit repository or Metasploit module has been found for this CVE yet.
Weakness Classification and Attack Patterns (CWE & CAPEC)
CWE - Common Weakness Enumeration
While CVE identifies specific instances of vulnerabilities, CWE categorises the common flaws or weaknesses that can lead to vulnerabilities. CVE-2026-34831 is associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification (CAPEC) stores attack patterns, which are descriptions of the common attributes and approaches employed by adversaries to exploit the CVE-2026-34831 weaknesses.
Attack Vector and Accessibility
Official Sources and Advisories
Similar Vulnerabilities
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