CVE-2026-33658Network attack vector

CPU exhaustion via unbounded multi-range processing

Published Mar 26, 2026 · Updated Mar 26, 2026

Denial of service in Rails Active Storage before 7.2.3.1, 8.0.0 through 8.0.4, and 8.1.0 through 8.1.2 allows remote attackers to exhaust CPU. The proxy streaming concern passes every range from an unbounded Range header through Rack::Utils.get_byte_ranges and builds multipart output for each range. Proxy mode and a valid signed blob URL are required; thousands of small ranges impose disproportionate processing and can interrupt the Rails service.

CVSS severity6.5
Medium
EPSS probability0.43%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Denial of service in Rails Active Storage before 7.2.3.1, 8.0.0 through 8.0.4, and 8.1.0 through 8.1.2 allows remote attackers to exhaust CPU. The proxy streaming concern passes every range from an unbounded Range header through Rack::Utils.get_byte_ranges and builds multipart output for each range. Proxy mode and a valid signed blob URL are required; thousands of small ranges impose disproportionate processing and can interrupt the Rails service.

The record

CVE
CVE-2026-33658
Published
Mar 26, 2026
Updated
Mar 26, 2026
Vendor
Rails
Product
Active Storage
Classifications
CWE-770, CAPEC-469, T1499.003
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Mar 26, 2026CVE publishedPublication date reported by the CVE source.
  2. Mar 26, 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=< 7.2.3.1
  2. Affected versionversion=>= 8.0.0, < 8.0.4.1
  3. Affected versionversion=>= 8.1.0, < 8.1.2.1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Rails · Active Storageversion=< 7.2.3.1; version=>= 8.0.0, < 8.0.4.1; version=>= 8.1.0, < 8.1.2.1

Published CVSS scores

2.3GitHub, Inc.CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:U
6.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:L/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.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-770Allocation of Resources Without Limits or Throttling
CAPEC-469HTTP DoS
T1499.003Endpoint Denial of Service: Application Exhaustion Flood

Public exploit references

No public exploit references are available in this record.

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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