GHSA-hqj5-cw9f-rx67: swagger-typescript-api vulnerable to code injection via unescaped `servers[0].url` in fetch http-client template
Summary
swagger-typescript-api interpolates servers[0].url directly into a TypeScript class-body field initializer of the generated fetch HttpClient (templates/base/http-clients/fetch-http-client.ejs:75), without any escaping. A malicious URL containing a " closes the string literal that initializes public baseUrl and exposes the surrounding *class body* to injection. The most direct exploit declares a new static field whose initializer is an async IIFE — TypeScript evaluates static field initializers at class definition time, which is at module load. A consumer who imports the generated client (or anything that transitively imports it) executes the injected code with no further interaction — no instantiation, no method call, no use of the baseUrl. The attacker controls the OpenAPI spec; the victim is whoever runs the generator and imports the result.
This is the highest-impact sink in the package: the trigger requires only a bare import of the generated module.
Details
createApiConfig in src/code-gen-process.ts:591 sets the templated baseUrl from the spec without sanitization:
return {
...
baseUrl: serverUrl, // <-- serverUrl = swaggerSchema.servers[0].url, raw
...
};
The fetch http-client template (templates/base/http-clients/fetch-http-client.ejs:75) then interpolates that value into a TS string literal that initializes a public class-body field of the generated HttpClient:
export class HttpClient<SecurityDataType = unknown> {
public baseUrl: string = "<%~ apiConfig.baseUrl %>";
private securityData: SecurityDataType | null = null;
...
}
<%~ %> is Eta's raw, unescaped interpolation. The codebase's only escape function — escapeJSDocContent (src/schema-parser/schema-formatters.ts:127) — only replaces */ and is not applied to this path.
TypeScript class-body grammar permits any number of field declarations and static blocks between { and }. A spec value of the form:
URL"; static _pwn = (IIFE)(); public x: string = "
produces the following class body:
exp
Details
Original advisory: https://github.com/advisories/GHSA-hqj5-cw9f-rx67
Exploitation outlook
EPSS (FIRST.org) estimates each CVE’s probability of exploitation in the next 30 days — here is the CSIRTS.com read on those numbers.
- Low exploitation riskCVE-2026-546620.27% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 19% of all scored CVEs.
Referenced CVEs
| CVE | CSIRTS overview | External |
|---|---|---|
| CVE-2026-54662 | coverage & exploitation status | NVD · CVE.org |
Same CVEs, other sources
How other CERTs, PSIRTs and databases cover the vulnerabilities in this advisory.
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