CVE-2026-34829: rack Uncontrolled Resource Consumption
Vulnerability summary
CVE-2026-34829 is a high (CVSS 7.5) Uncontrolled Resource Consumption vulnerability in rack. EPSS estimates a 0.66% chance of exploitation in the next 30 days, higher than 50.8% of scored vulnerabilities.
Advisory lineage
Upstream 0 · Downstream 5 · Related 6Timeline
- 02-04-2026PublishedVulnerability first disclosed.
- 15-07-2026Last modifiedVulnerability information updated.
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.
CVSS metrics
7 scores · 7 sources · 1 version- OSV · UbuntuEcosystem advisory · calculated7.5HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- OSV · DebianEcosystem advisory · calculated7.5HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- OSV · WolfiEcosystem advisory · calculated7.5HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- OSV · ChainguardEcosystem advisory · calculated7.5HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- OSV · RubygemsEcosystem advisory · calculated7.5HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- NVDNIST7.5HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
EPSS trend
Probability
0.66%
Chance of exploitation in the next 30 days
Percentile
51%
Versus all other CVEs
30-day change
+0.29 pp
From 0.37% on 21-09-2026
Known exploited
Compare KEV catalogsNot in any of the 3 tracked catalogs.
Public exploits
0 foundNo public exploits indexed.
Weaknesses
CWE · root cause- CWE-400Uncontrolled Resource ConsumptionThe product does not properly control the allocation and maintenance of a limited resource.
- CWE-770Allocation of Resources Without Limits or ThrottlingThe product allocates a reusable resource or group of resources on behalf of an actor without imposing any intended restrictions on the size or number of resources that can be allocated.
Affected systems
Chainguard57 products
- gitlab-exporter-18.10< 18.10.3-r0
- gitlab-exporter-18.7All versions (No fix recorded)
- gitlab-exporter-18.8< 18.8.9-r0
- gitlab-exporter-18.9< 18.9.5-r0
- gitlab-rails-ce-18.1< 18.1.6-r13
Wolfi8 products
- kube-fluentd-operator< 1.18.2-r67 | < 1.18.2-r60
- logstash-9.3< 9.3.3-r2
- logstash-9.3-iamguarded-compat< 9.3.3-r2
- logstash-9.3-with-output-opensearch< 9.3.3-r2
- ruby3.2-rack-2.2< 2.2.23-r0
Debian1 product
- ruby-rack< 2.2.22-0+deb12u2 | < 3.1.20-0+deb13u2 | < 3.2.6-2
Rack1 product
- rack≥ 3.0.0.beta1, < 3.1.21 | < 2.2.23 | ≥ 3.0.0, < 3.1.21 | ≥ 3.2.0, < 3.2.6
RubyGems1 product
- rack< 2.2.23 | ≥ 3.0.0.beta1, < 3.1.21 | ≥ 3.2.0, < 3.2.6
Ubuntu1 product
- ruby-rackAll versions (No fix recorded) | < 2.1.4-5ubuntu1.2+esm3 | < 2.2.7-1ubuntu0.7 | < 3.1.16-0.1ubuntu0.3
6 vendors · 69 products
References
12 links- github.com/rack/rack/security/advisories/GHSA-8vqr-qjwx-82mwX Refsource CONFIRMREPORTAdvisoryWEBVendor Advisory
Show all 12 references
- github.com/rack/rackPACKAGE