CVE-2026-27633 TinyWeb has Unbounded Content-Length Memory Exhaustion (DoS)
Unauthenticated attackers can crash the TinyWeb server by sending HTTP requests with excessively large Content-Length headers, causing memory exhaustion.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-27633?
CVE-2026-27633 is a high-severity denial of service vulnerability in maximmasiutin TinyWeb, published on 25 Feb 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
TinyWeb is a web server (HTTP, HTTPS) written in Delphi for Win32. Versions prior to version 2.02 have a Denial of Service (DoS) vulnerability via memory exhaustion. Unauthenticated remote attackers can send an HTTP POST request to the server with an exceptionally large `Content-Length` header (e.g., `2147483647`). The server continuously allocates memory for the request body (`EntityBody`) while streaming the payload without enforcing any maximum limit, leading to all available memory being consumed and causing the server to crash. Anyone hosting services using TinyWeb is impacted. Version 2.02 fixes the issue. The patch introduces a `CMaxEntityBodySize` limit (set to 10MB) for the maximum size of accepted payloads. As a temporary workaround if upgrading is not immediately possible, consider placing the server behind a Web Application Firewall (WAF) or reverse proxy (like nginx or Cloudflare) configured to explicitly limit the maximum allowed HTTP request body size (e.g., `client_max_body_size` in nginx).
Which versions are affected by CVE-2026-27633?
It affects 1 product.
Products include Ritlabs Tinyweb.
How do I fix CVE-2026-27633?
No fix has been published for CVE-2026-27633 yet. Limit exposure of the affected software until one is available.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-27633 being exploited?
There is no known exploitation of CVE-2026-27633 in the wild and no public exploit code.
Other vulnerabilities in maximmasiutin TinyWeb
- CVE-2026-27613 CGI Parameter Injection (Bypass of STRICT_CGI_PARAMS and EscapeShellParam)
- CVE-2026-22781 TinyWeb CGI Command Injection
- CVE-2026-28497 TinyWeb: Integer Overflow in `_Val` (HTTP Request Smuggling)
- CVE-2026-29046 TinyWeb: HTTP Header Control Character Injection into CGI Environment
- CVE-2026-27630 TinyWeb vulnerable to Remote Denial of Service via Thread/Connection Exhaustion (Slowloris)
Sources
Also known as GHSA-992w-gmcm-fmgr.