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CVE-2026-34829
ANC
High

Rack is a modular Ruby web server interface. Prior to versions 2.2.23, 3.1.21, and 3.2.6, Rack::Multipart::Parser only wraps the request bo…

CVSS
7.5
High
EPSS
0.00
p20
Published
2026-01-01
Updated
2026-01-01
Description

Rack is a modular Ruby web server interface. Prior to versions 2.2.23, 3.1.21, and 3.2.6, Rack::Multipart::Parser only wraps the request body in a BoundedIO when CONTENT_LENGTH is present. When a multipart/form-data request is sent without a Content-Length header, such as with HTTP chunked transfer encoding, multipart parsing continues until end-of-stream with no total size limit. For file parts, the uploaded body is written directly to a temporary file on disk rather than being constrained by the buffered in-memory upload limit. An unauthenticated attacker can therefore stream an arbitrarily large multipart file upload and consume unbounded disk space. This results in a denial of service condition for Rack applications that accept multipart form data. This issue has been patched in versions 2.2.23, 3.1.21, and 3.2.6.

Tags · CWE
Pre-auth
CWE-400
CAPEC-147
CAPEC-227
CAPEC-492
Affected products
Rack < 2.2.23Rack 3.0.0–3.1.21Rack 3.2.0–3.2.6
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Timeline
2026-01-01
Published
2026-01-01
Updated
CVSS 3.1 breakdown
Attack Vector
AV: N
Network (N)
Attack Complexity
AC: L
Low (L)
Privileges Required
PR: N
None (N)
User Interaction
UI: N
None (N)
Scope
S: U
Unchanged (U)
Confidentiality Impact
C: N
None (N)
Integrity Impact
I: N
None (N)
Availability Impact
A: H
High (H)
Exploit indicators
EPSS
0.001 · p20
Known exploited (KEV)
No
MITRE ATT&CK
Inferred via CAPEC
└ via CAPEC-227 · CWE-400
Known exploits — Сканер-ВС
No Сканер-ВС checks registered for this vulnerability yet.
Affected software
ProductVendorStatus
Tracked
ruby-rackTracked
rack*Tracked
Source databases
ANC
DEB
CVE
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