What’s Vulnerable › Vulnerabilities

CVE-2026-27633: TinyWeb has Unbounded Content-Length Memory Exhaustion (DoS)

• Severity: high (CVSS 7.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.5% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-02-26 · updated 2026-06-17
• Weakness: CWE-400

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).

Affected products

• maximmasiutin TinyWeb: before 2.02 — fixed in 2.02

How to fix

Upgrade to a fixed version: maximmasiutin TinyWeb 2.02. Check the vendor advisory for mitigations.

References

• https://github.com/maximmasiutin/TinyWeb/commit/1cb5a1d
• https://github.com/maximmasiutin/TinyWeb/security/advisories/GHSA-992w-gmcm-fmgr
• https://www.masiutin.net/tinyweb-cve-2026-27633.html

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