PT-2026-40607 · Bandit · Bandit

Jonatan Männchen + 2 · Published 2026-05-13 · Updated 2026-05-19 · CVE-2026-39803

Positive Technologies (AI Summary)

CVSS v4.0

8.7

High

Base vector

AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N

Name of the Vulnerable Software and Affected Versions bandit versions 1.4.0 through 1.11.0

Description An unauthenticated remote attacker can cause a denial of service via memory exhaustion. The read data/2 function in Elixir.Bandit.HTTP1.Socket ignores the :length option when processing HTTP/1 chunked request bodies. Specifically, the do read chunked data!/5 function buffers every received chunk into an iolist without capping the accumulated body at the configured limit, materializing the entire body as a single binary. Since this process occurs before routing and authentication in standard Phoenix endpoints, sending a single POST request with a Transfer-Encoding: chunked header and an arbitrarily large body can exhaust the BEAM process memory, leading to termination by the operating system's Out-Of-Memory (OOM) killer.

Recommendations Update bandit to version 1.11.1.

Exploit

Fix

Allocation of Resources Without Limits

Weakness Enumeration

CWE-770

Related Identifiers

CVE-2026-39803

GHSA-9Q9Q-324X-93R2

Affected Products

Bandit

References · 8

• 🔥 https://github.com/mtrudel/bandit/security/advisories/GHSA-9q9q-324x-93r2 · Exploit
• https://github.com/mtrudel/bandit/commit/ae3520dfdbfab115c638f8c7f6f6b805db34e1ab · Patch
• https://osv.dev/vulnerability/GHSA-9q9q-324x-93r2 · Vendor Advisory
• https://nvd.nist.gov/vuln/detail/CVE-2026-39803 · Security Note
• https://osv.dev/vulnerability/EEF-CVE-2026-39803 · Vendor Advisory
• https://github.com/mtrudel/bandit · Note
• https://hex.pm/packages/bandit · Note
• https://cna.erlef.org/cves/CVE-2026-39803.html · Note