OxBat opened a new pull request, #587:
URL: https://github.com/apache/logging-log4cxx/pull/587
### Summary
I identified a Denial of Service vulnerability in `TelnetAppender`.
The appender performs synchronous blocking I/O on the logging thread.
**The Attack (Slow Consumer):**
If a connected Telnet client refuses to read data (e.g., malicious
"Slowloris" style attack or network stall), the server's TCP Send Buffer fills
up.
Once full, the `write()` call blocks indefinitely because there was no
timeout configured.
Since Appenders are synchronized (mutex locked), this single blocked thread
halts ALL logging threads, causing the entire application to hang/freeze.
**The Fix:**
1. **Socket API:** Added `virtual void setSoTimeout(int)` to the `Socket`
interface.
2. **TelnetAppender:** * Calls `newClient->setSoTimeout(1000)` immediately
upon connection.
* Catches `InterruptedIOException` in the `write()` loop. If a write
blocks for > 1000ms, the connection is considered dead/malicious and is dropped
to unblock the application.
### Impact
This prevents a trivial remote DoS where a single unauthenticated connection
could freeze the host application.
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