Eclipse Jetty: Proxy credential disclosure via forged 407 in HTTPS tunnel
Summary
Eclipse Jetty's HttpClient (jetty-client) accepts any 407 Proxy Authentication Required response after an HTTPS CONNECT tunnel is established, even if it comes from the destination server rather than the proxy. A malicious or compromised HTTPS server can send a forged 407 challenge, and Jetty then resends the request with the configured proxy username and password inside the TLS tunnel. The attacker can read these credentials, but no code execution is involved. The flaw requires a Jetty HttpClient application that uses proxy authentication and connects to an untrusted HTTPS endpoint.
Affected
- org.eclipse.jetty:jetty-client 12.1.0 to 12.1.12
- 12.0.0 to 12.0.38
- 11.0.0 to 11.0.32
- 10.0.0 to 10.0.32
- 9.4.0 to 9.4.64
Fixed in
- 12.1.13
- 12.0.39
- 11.0.33
- 10.0.33
- 9.4.65
(Patched versions as listed in GHSA-r2c5-3p8g-wpvw. Some release notes do not name this CVE, so verify against the advisory.)
Workaround
- No vendor-documented workaround found.
- Avoid authenticated forward proxies for HTTPS calls to untrusted destinations.
- Restrict outbound connections to known endpoints.
- Use a dedicated low-privilege proxy account.
Exploitation
- Not listed as known exploited (CISA KEV: no).
- CISA SSVC lists exploitation as 'poc' and automatable as 'no'.
- No public proof of concept found in research. EPSS about 0.0032 (low).
Our recommendation
- Inventory applications and software that embed jetty-client and check their versions.
- Upgrade to a fixed version listed above, or ask software vendors for a patched build.
- Where patching is not possible, apply the workarounds and limit proxy credentials to the minimum needed.
- Rotate proxy credentials if an affected client has connected to an untrusted HTTPS host.
- Monitor proxy logs for unexpected authentication activity.
Public exploits
PoC-in-GitHub, Metasploit and Exploit-DB list nothing for this CVE.
Research sources
- GitHub Security Advisory GHSA-r2c5-3p8g-wpvw github.com
- Eclipse CVE assignment work item #238 gitlab.eclipse.org
- HeroDevs vulnerability directory entry www.herodevs.com
- Vulners NVD record CVE-2026-77711 vulners.com
- VulDB entry 420567 vuldb.com
- Strix CVE record CVE-2026-77711 www.strix.ai
- Jetty release 12.1.13 github.com
- Jetty release 12.0.39 github.com
Researched and written up in English and German by an AI (Claude by Anthropic) based on NVD, CISA, EPSS and the sources listed. The vendor information is authoritative. Researched on 1 Nov 2026, 16:02.
Original description (NVD)
When Jetty's `HttpClient` make a request to a server through a forward proxy, the server may reply with a 407 (Proxy Authentication Required). The client mistakenly interprets the 407 as coming from the proxy, so it re-sends the request with the `Proxy-Authentication` header, which arrives to the server, that now has access to the proxy credentials.
Sources
The tracker combines official, freely usable data sources – updated continuously:
- NVD (NIST) – CVEs, rating (CVSS), affected products
- CISA KEV – vulnerabilities confirmed by CISA as actively exploited
- CISA Vulnrichment – CISA assessment (SSVC) in the official CVE record
- FIRST EPSS – probability of exploitation
- Microsoft MSRC – Patch Tuesday: vulnerabilities, severity, updates
- PoC-in-GitHub – public proof-of-concept repositories
- Metasploit (Rapid7) – modules of the Metasploit Framework
- Exploit-DB (OffSec) – archive of public exploits (links only)
- Patch days: official vendor pages (linked per vendor) (Vendor patch days)
This product uses data from the NVD API but is not endorsed or certified by the NVD. EPSS data © FIRST.org.
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