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VulnerabilityPublished Updated

CVE-2026-39803: mtrudel bandit · Unthrottled Resource Allocation

Affects mtrudel banditSource CVE Database V5

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Not known to be exploited · CVSS 8.7 High : upgrade to 1.11.1 soon.

Data as of 30 Oct 2026, 11:52 UTC

CVSS 4.0 base score
8.7High
How severe the flaw is on the 0–10 CVSS scale.
EPSS
0.6% chance of exploitation in 30 days – higher than 50% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch
Available – fixed in 1.11.1, ae3520dfdbfab115c638f8c7f6f6b805db34e1ab
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 13 May 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 30 Oct 2026.

What to do

Upgrade bandit and mtrudel/bandit to 1.11.1; bandit to ae3520dfdbfab115c638f8c7f6f6b805db34e1ab.

Affected software

ProductAffectedFixed in
mtrudelbanditAffected
  • >=1.4.0 <1.11.1
Fixed in
  • 1.11.1
mtrudelbanditAffected
  • ≥ 903e209a521bc216b9f9065c01ae9a0cac2d5a10, < ae3520dfdbfab115c638f8c7f6f6b805db34e1ab
Fixed in
  • ae3520dfdbfab115c638f8c7f6f6b805db34e1ab
Hexmtrudel/banditpkg:hex/mtrudel/banditOther threatsAffected
  • <1.11.1
Fixed in
  • 1.11.1
Hexbanditpkg:hex/banditOther threatsAffected
  • >=1.4.0 <1.11.1
Fixed in
  • 1.11.1

CPE configurations (1)

  • cpe:2.3:a:mtrudel:bandit:*:*:*:*:*:*:*:*

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

If you cannot patch yet, consider implementing network-level protections such as limiting request sizes or blocking chunked transfer encoding requests from untrusted sources. Monitoring for unusually large chunked requests may help detect exploitation attempts. Avoid relying solely on application-level size limits for chunked bodies in affected versions.

Description

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.

References

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