{"timestamp":"2026-05-13T14:41:58.440838Z","id":"CVE-2026-39803","options":[{"exploitation":"poc"},{"automatable":"yes"},{"technicalImpact":"partial"}],"role":"CISA Coordinator","version":"2.0.3"}

[{"vendor":"mtrudel","product":"bandit","defaultStatus":"unaffected","collectionURL":"https://repo.hex.pm","packageName":"bandit","cpes":["cpe:2.3:a:mtrudel:bandit:*:*:*:*:*:*:*:*"],"modules":["'Elixir.Bandit.HTTP1.Socket'"],"programFiles":["lib/bandit/http1/socket.ex"],"programRoutines":[{"name":"'Elixir.Bandit.HTTP1.Socket':read_data/2"},{"name":"'Elixir.Bandit.HTTP1.Socket':do_read_chunked_data!/5"}],"repo":"https://github.com/mtrudel/bandit","packageURL":"pkg:hex/bandit","versions":[{"version":"1.4.0","lessThan":"1.11.1","versionType":"semver","status":"affected"}]},{"vendor":"mtrudel","product":"bandit","defaultStatus":"unaffected","collectionURL":"https://github.com","packageName":"mtrudel/bandit","cpes":["cpe:2.3:a:mtrudel:bandit:*:*:*:*:*:*:*:*"],"modules":["'Elixir.Bandit.HTTP1.Socket'"],"programFiles":["lib/bandit/http1/socket.ex"],"programRoutines":[{"name":"'Elixir.Bandit.HTTP1.Socket':read_data/2"},{"name":"'Elixir.Bandit.HTTP1.Socket':do_read_chunked_data!/5"}],"repo":"https://github.com/mtrudel/bandit","packageURL":"pkg:github/mtrudel/bandit","versions":[{"version":"903e209a521bc216b9f9065c01ae9a0cac2d5a10","lessThan":"ae3520dfdbfab115c638f8c7f6f6b805db34e1ab","versionType":"git","status":"affected"}]}]

AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

OR
          *cpe:2.3:a:mtrudel:bandit:*:*:*:*:*:*:*:* versions from (including) 1.4.0 up to (excluding) 1.11.1

CISA-ADP: https://github.com/mtrudel/bandit/security/advisories/GHSA-9q9q-324x-93r2 Types: Exploit, Vendor Advisory

EEF: https://cna.erlef.org/cves/CVE-2026-39803.html Types: Third Party Advisory

EEF: https://github.com/mtrudel/bandit/commit/ae3520dfdbfab115c638f8c7f6f6b805db34e1ab Types: Patch

EEF: https://github.com/mtrudel/bandit/security/advisories/GHSA-9q9q-324x-93r2 Types: Exploit, Vendor Advisory

EEF: https://osv.dev/vulnerability/EEF-CVE-2026-39803 Types: Third Party Advisory

https://github.com/mtrudel/bandit/security/advisories/GHSA-9q9q-324x-93r2

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.

AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

CWE-770

https://cna.erlef.org/cves/CVE-2026-39803.html

https://github.com/mtrudel/bandit/commit/ae3520dfdbfab115c638f8c7f6f6b805db34e1ab

https://github.com/mtrudel/bandit/security/advisories/GHSA-9q9q-324x-93r2

https://osv.dev/vulnerability/EEF-CVE-2026-39803