CVE-2026-66339
Libsoup: libsoup: proxy credentials leak to destination server via proxy-authorization header in connect tunnels
What happened?
A flaw was found in libsoup. After a CONNECT tunnel is established through an HTTP proxy, libsoup incorrectly attaches the Proxy-Authorization header to subsequent HTTPS requests sent through that tunnel to the destination server. This allows the destination server to capture proxy credentials, leading to information disclosure.
Affected software and versions
| Software | Version information | Fixed version |
|---|---|---|
| libsoup3Red Hat | Default status: affected | See vendor advisory |
| libsoupRed Hat | Default status: affected | See vendor advisory |
| libsoupRed Hat | Default status: affected | See vendor advisory |
| libsoupRed Hat | Default status: affected | See vendor advisory |
| libsoupRed Hat | Default status: affected | See vendor advisory |
Version information comes from the source record and can include unaffected products and exceptions. Distribution packages may contain backported fixes: an older upstream version alone does not prove a server is affected.
Is it being exploited?
This CVE was not listed in the CISA catalogue at our last retrieval. This does not establish that exploitation is absent.
How to respond
- Confirm the product, installed package version, and any configuration requirements in the vendor advisory.
- Follow the vendor’s remediation or workaround guidance in the references below. Structured fixed-version data is unavailable here; the publisher’s description may include a fix or workaround.
- Restart affected services if required, then verify the running version. Known exploitation may warrant investigation as well as patching.