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CVE Vulnerability Details :
CVE-2026-39803
PUBLISHED
More InfoOfficial Page
Assigner-EEF
Assigner Org ID-6b3ad84c-e1a6-4bf7-a703-f496b71e49db
View Known Exploited Vulnerability (KEV) details
Published At-13 May, 2026 | 13:36
Updated At-13 May, 2026 | 18:27
Rejected At-
▼CVE Numbering Authority (CNA)
HTTP/1 chunked body reader ignores length cap in bandit

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.

Affected Products
Vendor
mtrudel
Product
bandit
Collection URL
https://repo.hex.pm
Package Name
bandit
Repo
https://github.com/mtrudel/bandit
CPEs
  • cpe:2.3:a:mtrudel:bandit:*:*:*:*:*:*:*:*
Modules
  • 'Elixir.Bandit.HTTP1.Socket'
Program Files
  • lib/bandit/http1/socket.ex
Program Routines
  • 'Elixir.Bandit.HTTP1.Socket':read_data/2
  • 'Elixir.Bandit.HTTP1.Socket':do_read_chunked_data!/5
Default Status
unaffected
Versions
Affected
  • From 1.4.0 before 1.11.1 (semver)
Vendor
mtrudel
Product
bandit
Collection URL
https://github.com
Package Name
mtrudel/bandit
Repo
https://github.com/mtrudel/bandit
CPEs
  • cpe:2.3:a:mtrudel:bandit:*:*:*:*:*:*:*:*
Modules
  • 'Elixir.Bandit.HTTP1.Socket'
Program Files
  • lib/bandit/http1/socket.ex
Program Routines
  • 'Elixir.Bandit.HTTP1.Socket':read_data/2
  • 'Elixir.Bandit.HTTP1.Socket':do_read_chunked_data!/5
Default Status
unaffected
Versions
Affected
  • From 903e209a521bc216b9f9065c01ae9a0cac2d5a10 before ae3520dfdbfab115c638f8c7f6f6b805db34e1ab (git)
Problem Types
TypeCWE IDDescription
CWECWE-770CWE-770 Allocation of Resources Without Limits or Throttling
Type: CWE
CWE ID: CWE-770
Description: CWE-770 Allocation of Resources Without Limits or Throttling
Metrics
VersionBase scoreBase severityVector
4.08.7HIGH
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
Version: 4.0
Base score: 8.7
Base severity: HIGH
Vector:
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
Metrics Other Info
Impacts
CAPEC IDDescription
CAPEC-130CAPEC-130 Excessive Allocation
CAPEC ID: CAPEC-130
Description: CAPEC-130 Excessive Allocation
Solutions

Configurations

Workarounds

Exploits

Credits

finder
Peter Ullrich
remediation developer
Mat Trudel
analyst
Jonatan Männchen
Timeline
EventDate
Replaced By

Rejected Reason

References
HyperlinkResource
https://github.com/mtrudel/bandit/security/advisories/GHSA-9q9q-324x-93r2
vendor-advisory
related
https://cna.erlef.org/cves/CVE-2026-39803.html
related
https://osv.dev/vulnerability/EEF-CVE-2026-39803
related
https://github.com/mtrudel/bandit/commit/ae3520dfdbfab115c638f8c7f6f6b805db34e1ab
patch
Hyperlink: https://github.com/mtrudel/bandit/security/advisories/GHSA-9q9q-324x-93r2
Resource:
vendor-advisory
related
Hyperlink: https://cna.erlef.org/cves/CVE-2026-39803.html
Resource:
related
Hyperlink: https://osv.dev/vulnerability/EEF-CVE-2026-39803
Resource:
related
Hyperlink: https://github.com/mtrudel/bandit/commit/ae3520dfdbfab115c638f8c7f6f6b805db34e1ab
Resource:
patch
▼Authorized Data Publishers (ADP)
CISA ADP Vulnrichment
Affected Products
Metrics
VersionBase scoreBase severityVector
Metrics Other Info
Impacts
CAPEC IDDescription
Solutions

Configurations

Workarounds

Exploits

Credits

Timeline
EventDate
Replaced By

Rejected Reason

References
HyperlinkResource
https://github.com/mtrudel/bandit/security/advisories/GHSA-9q9q-324x-93r2
exploit
Hyperlink: https://github.com/mtrudel/bandit/security/advisories/GHSA-9q9q-324x-93r2
Resource:
exploit
Details not found