CVE-2026-34829Rack: Denial of Service via Unbounded Multipart File Upload Without Content-Length
Updated under an hour ago ()
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It affects rack and 3 other products. Add what you run to find out whether that includes you.
No exploitation reported and no EPSS estimate yet.
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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
- 7.5 HIGH (v3.1, CNA)CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- Weakness (CWE)
- CWE-400, CWE-770
- Known exploited
- Not in CISA's KEV catalog
- EPSS (exploitation in the next 30 days)
- Not loaded for this CVE
- Assigned by
- GitHub_M
- NVD analysis
- Modified
- Record last updated
- Jul 14, 2026
- First seen by InfoSec Signals
- Oct 9, 2026
Affected products
rack rack rack:rack (from the name) | before 2.2.23; from 3.0.0.beta1, < 3.1.21; from 3.2.0, < 3.2.6 | CNA record |
Red Hat Logging Subsystem for Red Hat OpenShift redhat:logging | 5 | CISA ADP |
Red Hat Red Hat 3scale API Management Platform 2 redhat:red_hat_3scale_amp | 2 | CISA ADP |
Red Hat Red Hat Enterprise Linux 10 redhat:enterprise_linux | 10 | CISA ADP |
rack rack rack:rack | before 2.2.23; from 3.0.0 before 3.1.21; from 3.2.0 before 3.2.6 | NVD |
References
- https://github.com/rack/rack/security/advisories/GHSA-8vqr-qjwx-82mwx-refsource-confirm, vendor-advisory
- https://access.redhat.com/security/cve/CVE-2026-34829
- https://bugzilla.redhat.com/show_bug.cgi?id=2454488
- https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-34829.json
The CVE record on cve.org NVD's entry
The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.