CVE-2026-66753 Vulnerability Analysis & Exploit Details

CVE-2026-66753 Vulnerability Summary

CVE-2026-66753: tiny-http through 0.12.0 contains an HTTP header injection vulnerability that allows attackers to inject carriage return (0x0D) and line feed (0x0A) bytes into HTTP header values on both request and response sides due to insufficient validation in header parsing and serialization. Attackers can exploit this injection primitive to perform response splitting, cache poisoning, session fixation via Set-Cookie injection, security header override, and request smuggling against line-feed-tolerant backends.

CVE-2026-66753 References

External References

• https://github.com/theopaid/HTTP-Header-Injection-via-Unvalidated-CR-and-LF-in-Header-Values-tiny_http-/tree/master
• https://www.vulncheck.com/advisories/tiny-http-http-response-splitting-via-header-injection

CWE Common Weakness Enumeration

CAPEC Common Attack Pattern Enumeration and Classification

• HTTP Request Splitting CAPEC-105 An adversary abuses the flexibility and discrepancies in the parsing and interpretation of HTTP Request messages by different intermediary HTTP agents (e.g., load balancer, reverse proxy, web caching proxies, application firewalls, etc.) to split a single HTTP request into multiple unauthorized and malicious HTTP requests to a back-end HTTP agent (e.g., web server). See CanPrecede relationships for possible consequences.
• Accessing/Intercepting/Modifying HTTP Cookies CAPEC-31 This attack relies on the use of HTTP Cookies to store credentials, state information and other critical data on client systems. There are several different forms of this attack. The first form of this attack involves accessing HTTP Cookies to mine for potentially sensitive data contained therein. The second form involves intercepting this data as it is transmitted from client to server. This intercepted information is then used by the adversary to impersonate the remote user/session. The third form is when the cookie's content is modified by the adversary before it is sent back to the server. Here the adversary seeks to convince the target server to operate on this falsified information.
• HTTP Response Splitting CAPEC-34 An adversary manipulates and injects malicious content, in the form of secret unauthorized HTTP responses, into a single HTTP response from a vulnerable or compromised back-end HTTP agent (e.g., web server) or into an already spoofed HTTP response from an adversary controlled domain/site. See CanPrecede relationships for possible consequences.
• AJAX Footprinting CAPEC-85 This attack utilizes the frequent client-server roundtrips in Ajax conversation to scan a system. While Ajax does not open up new vulnerabilities per se, it does optimize them from an attacker point of view. A common first step for an attacker is to footprint the target environment to understand what attacks will work. Since footprinting relies on enumeration, the conversational pattern of rapid, multiple requests and responses that are typical in Ajax applications enable an attacker to look for many vulnerabilities, well-known ports, network locations and so on. The knowledge gained through Ajax fingerprinting can be used to support other attacks, such as XSS.

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