CVE-2026-39806
HighSummary
CVE-2026-39806 vulnerability in mtrudel bandit allows remote denial of service via worker process exhaustion. The issue occurs in the do_read_chunked_data!/5 function, which does not terminate correctly when trailer fields are present in chunked requests.
Risk Assessment
An attacker can exploit this vulnerability to block the server, leading to unresponsiveness to all further connections. A handful of concurrent connections is sufficient to exhaust the Bandit worker pool.
Recommendation
It is recommended to monitor and limit the number of concurrent connections and to update to the latest version of Bandit to minimize the risk associated with this vulnerability.
Other vulnerabilities in mtrudel bandit
See all- CVE-2026-39803High
CVE-2026-39803 in mtrudel bandit has a resource allocation without limits vulnerability that allows unauthenticated remote denial of service via memory exhaustion. The do_read_chunked_data!/5 function does not cap the size of buffered data, leading to memory overflow.
- CVE-2026-39804High
CVE-2026-39804 vulnerability in mtrudel bandit allows for remote denial of service via memory exhaustion when permessage-deflate compression is enabled in WebSocket. An unauthenticated attacker can send a specially crafted frame, leading to an out-of-memory kill.
Original NVD description (English source)
Loop with Unreachable Exit Condition ('Infinite Loop') vulnerability in mtrudel bandit allows unauthenticated remote denial of service via worker process exhaustion. 'Elixir.Bandit.HTTP1.Socket':do_read_chunked_data!/5 in lib/bandit/http1/socket.ex terminates only when the last-chunk line 0\r\n is followed immediately by the empty trailer line \r\n. RFC 9112 §7.1.2 permits zero or more trailer fields between them. When trailers are present, none of the match clauses fit: the catch-all arm computes a negative to_read, calls read_available!/2, receives <<>> on timeout, and tail-recurses with unchanged state. The worker process is pinned for the lifetime of the TCP connection. A handful of concurrent connections sending RFC-conformant chunked requests with trailer fields is sufficient to exhaust the Bandit worker pool and render the server unresponsive to all further traffic. No authentication, special headers, or large payload is required. Proxies such as NGINX and HAProxy legitimately