Medium · published May 13, 2026
Successfully using libcurl to do a transfer over a specific HTTP proxy
(`proxyA`) with **Digest** authentication and then changing the proxy host to
a second one (`proxyB`) for a second transfer, reusing the same handle, makes
libcurl wrongly pass on the `Proxy-Authorization:` header field meant for
`proxyA`, to `proxyB`.
| Product | Versions | Fixed in |
|---|---|---|
| haxx/curl | ≥ 7.12.0, < 8.20.0 | 8.20.0 |