CVE-2026-50018
Summary:
Remote post-serve actions use http.DefaultClient without any timeout configuration. When the remote endpoint is unreachable or intentionally slow (accepts TCP connection but never responds), each triggered proxy request spawns a goroutine that blocks indefinitely on http.DefaultClient.Do(). An attacker can cause unbounded goroutine accumulation leading to memory exhaustion and process crash (OOM kill). Unlike local post-serve action execution, this requires no binary execution, only a URL pointing to a non-responsive endpoint.
Details:
1. Remote actions executed in goroutines without timeout (core/hoverfly.go:224-228):
go postServeAction.Execute(result.Pair, journalIDChannel, hf.Journal)
Post-serve actions are executed in separate goroutines with no recovery wrapper.
2. HTTP client has no timeout (core/action/action.go:128-143):
req, err := http.NewRequest("POST", action.Remote, bytes.NewBuffer(pairViewBytes))
// ...
resp, err := http.DefaultClient.Do(req) // No timeout! Blocks forever.
http.DefaultClient has zero timeout by default in Go. If the remote server:
- Accepts the TCP connection but never sends a response
- Establishes TLS but never completes the handshake
- Uses TCP window size 0 (flow control stall)
...the goroutine blocks indefinitely. There is no context cancellation, no deadline, and no cleanup.
3. No goroutine limit or backpressure:
There is no limit on how many post-serve action goroutines can be active simultaneously. Each matching proxy request spawns a new one unconditionally.
4. The goroutine is never cleaned up:
The only exit path from Execute() is a successful (or failed) HTTP response. A non-responding server means the goroutine lives until the process is killed.
Environment:
- Hoverfly version: v1.12.7
- Operating System: macOS Darwin 25.4.0
- Go version: 1.26.2
- Configuration: Default (no flags required)
POC:
Step 1: Start a black-hole TCP listener (accepts connections, never responds)
Option A: Use ncat
ncat -l
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Advisory coverage (1)
External references
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