CVE-2026-39803Public exploitNetwork attack vector

Unauthenticated server crash via unbounded chunk buffering

Published May 13, 2026 · Updated May 13, 2026

Resource exhaustion in Mat Trudel Bandit 1.4.0 through 1.11.0 allows remote attackers to crash the server via a chunked HTTP/1 body. The chunked clause of Bandit.HTTP1.Socket.read_data/2 drops the caller-supplied length limit, accumulates every chunk into an iolist, and converts the full body into one binary. Plug.Parsers processes matching body content types before routing and authentication, so one unauthenticated request to any path can exhaust BEAM memory and trigger OS termination.

CVSS severity8.7
High
EPSS probability0.64%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Resource exhaustion in Mat Trudel Bandit 1.4.0 through 1.11.0 allows remote attackers to crash the server via a chunked HTTP/1 body. The chunked clause of Bandit.HTTP1.Socket.read_data/2 drops the caller-supplied length limit, accumulates every chunk into an iolist, and converts the full body into one binary. Plug.Parsers processes matching body content types before routing and authentication, so one unauthenticated request to any path can exhaust BEAM memory and trigger OS termination.

The record

CVE
CVE-2026-39803
Published
May 13, 2026
Updated
May 13, 2026
Vendor
Mat Trudel
Product
Bandit
Classifications
CWE-770, T1499
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. May 13, 2026CVE publishedPublication date reported by the CVE source.
  2. May 13, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=1.4.0 <1.11.1
  2. Affected versionversion=903e209a521bc216b9f9065c01ae9a0cac2d5a10 <ae3520dfdbfab115c638f8c7f6f6b805db34e1ab

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Mat Trudel · Banditversion=1.4.0 <1.11.1; version=903e209a521bc216b9f9065c01ae9a0cac2d5a10 <ae3520dfdbfab115c638f8c7f6f6b805db34e1ab

Published CVSS scores

8.7Erlang Ecosystem FoundationCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
7.5National Vulnerability DatabaseCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-770Allocation of Resources Without Limits or Throttling
T1499Endpoint Denial of Service

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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