GHSA-9q9q-324x-93r2 · Severity: high · Ecosystem: erlang — Bandit: Unauthenticated one-shot DoS via `Transfer-Encoding: chunked`
Allocation of Resources Without Limits or Throttling vulnerability in mtrudel bandit allows unauthenticated remote denial of service via memory exhaustion. The chunked clause of 'Elixir.Bandit.HTTP1.Socket':read_data/2 in lib/bandit/http1/socket.ex ignores the caller-supplied :length option when reading HTTP/1 chunked request bodies. Instead of capping the accumulated body at the configured limit (e.g. Plug.Parsers' default 8 MB), do_read_chunked_data!/5 buffers every received chunk into an iolist unconditionally and materializes the entire body as a single binary. The function always returns {:ok, body, ...}, so callers cannot interpose a 413 response. Because Plug.Parsers runs before routing and authentication in the standard Phoenix endpoint, an unauthenticated attacker needs no valid route or credentials. Sending a single Transfer-Encoding: chunked POST request with an arbitrarily large body to any path causes the BEAM process to exhaust available memory and be terminated by the OS OOM killer. The content-length path in the same function correctly enforces the limit and is not affected. This issue affects bandit: from 1.4.0 before 1.11.1.
Conclusion & alert: CVE-2026-39803 is rated High Exploit Risk (79.1/100): CVSS High severity, with medium exploitation likelihood (EPSS 1.41%). Core evidence: 1 public exploit reference(s) are indexed (Exploit-DB). EPSS rose +1.05% over the last day, indicating growing attacker interest. Mandatory action: Public exploits are available—assess exposure, apply mitigations, and prioritize patching.
Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.
| EDB-ID | Source | Kind | Published | Link |
|---|---|---|---|---|
| — | nvd_ref | exploit_tag | Exploit-DB ↗ |
EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).
| # | Date | Old EPSS score | New EPSS score | Delta (New - Old) |
|---|---|---|---|---|
| 1 | 2026-05-22 | 0.36% | 1.41% | +1.05% |
| 2 | 2026-05-19 | 0.31% | 0.36% | +0.06% |
| 3 | 2026-05-14 | — | 0.31% | — |
Full EPSS history (3 records total)
CVSS metrics for this CVE.
| Base score | Version | Severity | Vector | Exploitability | Impact | Score source |
|---|---|---|---|---|---|---|
| 8.7 | 4.0 | HIGH |
|
— | — | 6b3ad84c-e1a6-4bf7-a703-f496b71e49db |
| 7.5 | 3.1 | HIGH |
|
3.9 | 3.6 | [email protected] |
GHSA-9q9q-324x-93r2 · Severity: high · Ecosystem: erlang — Bandit: Unauthenticated one-shot DoS via `Transfer-Encoding: chunked`
| URL | Tags |
|---|---|
| https://cna.erlef.org/cves/CVE-2026-39803.html | Third Party Advisory |
| https://github.com/mtrudel/bandit/commit/ae3520dfdbfab115c638f8c7f6f6b805db34e1ab | Patch |
| https://github.com/mtrudel/bandit/security/advisories/GHSA-9q9q-324x-93r2 | Exploit Vendor Advisory |
| https://osv.dev/vulnerability/EEF-CVE-2026-39803 | Third Party Advisory |