CVE-2026-35036

Ech0 has Unauthenticated Server-Side Request Forgery in Website Preview Feature

• Verified: Unauthenticated callers can make the Ech0 process issue server-side HTTP(S) requests to internal/reserved targets reachable from that process (PoC Step 2: host-reachable listener reflected in JSON).
• Code-level: The full response is read into memory (io.ReadAll); only the title string is returned. Combined with default HTTP redirect following (standard http.Client behavior; not disabled here), the effective request graph is larger than a single URL.
• TLS: InsecureSkipVerify: true means misissued or intercepted TLS to internal HTTPS services is still accepted from the server’s perspective.
• Deployment-dependent: Where routing allows (typical cloud VMs), 169.254.169.254-class endpoints are in scope for the same code path; treat as *high.
• DOS(Denial of Service): reading the whole body into memory with io.ReadAll is a DoS vector if you point it at a massive file.

Untrusted input controls the target URL of a server-initiated request, which may reach internal services not otherwise accessible from outside. Typical impact: access to internal metadata services, internal APIs, or cloud credentials.

CVE-2026-35036 has a CVSS score of 7.5 (High). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (1.4.8-0.20260401031029-4ca56fea5ba4); upgrading removes the vulnerable code path.

Kodem intelligence

• Enforce SSRF-safe URL policy: allow only needed schemes/hosts; block link-local, metadata, and loopback unless explicitly required.
• Remove InsecureSkipVerify; use normal TLS verification.
• Limit redirects (disable or cap hops; re-validate each target).
• Add response size / timeout limits; optionally restrict egress at the network layer.

1. What is CVE-2026-35036? CVE-2026-35036 is a high-severity server-side request forgery (SSRF) vulnerability in github.com/lin-snow/ech0 (go), affecting versions < 1.4.8-0.20260401031029-4ca56fea5ba4. It is fixed in 1.4.8-0.20260401031029-4ca56fea5ba4. Untrusted input controls the target URL of a server-initiated request, which may reach internal services not otherwise accessible from outside.
2. How severe is CVE-2026-35036? CVE-2026-35036 has a CVSS score of 7.5 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of github.com/lin-snow/ech0 are affected by CVE-2026-35036? github.com/lin-snow/ech0 (go) versions < 1.4.8-0.20260401031029-4ca56fea5ba4 is affected.
4. Is there a fix for CVE-2026-35036? Yes. CVE-2026-35036 is fixed in 1.4.8-0.20260401031029-4ca56fea5ba4. Upgrade to this version or later.
5. Is CVE-2026-35036 exploitable, and should I be worried? Whether CVE-2026-35036 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2026-35036 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2026-35036? Upgrade github.com/lin-snow/ech0 to 1.4.8-0.20260401031029-4ca56fea5ba4 or later.