CVE-2026-34826Public exploitNetwork attack vector

Denial of service via unbounded byte-range count

Published Apr 2, 2026 · Updated Apr 2, 2026

Denial of service in Rack before 2.2.23, 3.0.0.beta1 through 3.1.20, and 3.2.0 through 3.2.5 allows remote attackers to exhaust resources. Rack::Utils.get_byte_ranges splits a comma-delimited Range value without capping its entry count, so overlapping one-byte ranges pass the aggregate-size check and drive repeated iteration, seeks, reads, allocations, and multipart output. Exposure requires an unauthenticated request to a file-serving path with byte-range support; repeated crafted requests consume CPU, memory, I/O, and bandwidth and reduce application availability.

CVSS severity5.3
Medium
EPSS probability0.38%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

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Summary

What happened

Denial of service in Rack before 2.2.23, 3.0.0.beta1 through 3.1.20, and 3.2.0 through 3.2.5 allows remote attackers to exhaust resources. Rack::Utils.get_byte_ranges splits a comma-delimited Range value without capping its entry count, so overlapping one-byte ranges pass the aggregate-size check and drive repeated iteration, seeks, reads, allocations, and multipart output. Exposure requires an unauthenticated request to a file-serving path with byte-range support; repeated crafted requests consume CPU, memory, I/O, and bandwidth and reduce application availability.

The record

CVE
CVE-2026-34826
Published
Apr 2, 2026
Updated
Apr 2, 2026
Vendor
Rack
Product
Rack
Classifications
CWE-770, CWE-400, T1499.003
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Apr 2, 2026CVE publishedPublication date reported by the CVE source.
  2. Apr 2, 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=< 2.2.23
  2. Affected versionversion=>= 3.0.0.beta1, < 3.1.21
  3. Affected versionversion=>= 3.2.0, < 3.2.6

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Rack · Rackversion=< 2.2.23; version=>= 3.0.0.beta1, < 3.1.21; version=>= 3.2.0, < 3.2.6

Published CVSS scores

7.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
5.3GitHub, Inc.CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

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
CWE-400Uncontrolled Resource Consumption
T1499.003Application Exhaustion Flood

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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