CVE-2026-32762 Rack: Forwarded Header semicolon injection enables Host and Scheme spoofing
Attackers can spoof Host and Scheme headers via semicolon injection in Rack's Forwarded header parsing, bypassing upstream proxy or WAF validation.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-32762?
CVE-2026-32762 is a medium-severity vulnerability in rack, published on 2 Apr 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
Rack is a modular Ruby web server interface. From versions 3.0.0.beta1 to before 3.1.21 and 3.2.0 to before 3.2.6, Rack::Utils.forwarded_values parses the RFC 7239 Forwarded header by splitting on semicolons before handling quoted-string values. Because quoted values may legally contain semicolons, a header can be interpreted by Rack as multiple Forwarded directives rather than as a single quoted for value. In deployments where an upstream proxy, WAF, or intermediary validates or preserves quoted Forwarded values differently, this discrepancy can allow an attacker to smuggle host, proto, for, or by parameters through a single header value. This issue has been patched in versions 3.1.21 and 3.2.6.
Weakness: CWE-436
Which versions are affected by CVE-2026-32762?
4 open source packages ship an affected version, including rack. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
rack RubyGems | From 3.0.0.beta1 | 3.1.21 |
rack RubyGems | From 3.0.0.beta1 | 3.1.21 |
rack RubyGems | From 3.2.0 | 3.2.6 |
rack RubyGems | From 3.2.0 | 3.2.6 |
Products include Rack Rack.
How do I fix CVE-2026-32762?
Upgrade rack to a fixed version for your release line: 3.1.21 or 3.2.6.
Is CVE-2026-32762 being exploited?
There is no known exploitation of CVE-2026-32762 in the wild and no public exploit code.
Other vulnerabilities in rack
- CVE-2026-34785 Rack: Local file inclusion in `Rack::Static` via URL Prefix Matching
- CVE-2026-34827 Rack: Algorithmic-Complexity DoS in Rack::Multipart::Parser
- CVE-2026-34829 Rack: Denial of Service via Unbounded Multipart File Upload Without Content-Length
- CVE-2026-22860 Rack has a Directory Traversal via Rack:Directory
- CVE-2025-61919 Rack is vulnerable to a memory-exhaustion DoS through unbounded URL-encoded body parsing
Sources
Also known as DEBIAN-CVE-2026-32762, GHSA-qfgr-crr9-7r49, MINI-2hx7-7g42-3qh9, MINI-5335-wxcw-wqw4, MINI-56gq-94r3-mc3j, MINI-7495-62jj-x2mv and 8 more.