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CVE-2026-125111

Rack: Multipart parsing allows DoS via unbounded scan buffer growth

publishedCWE-400

Rack is a modular Ruby web server interface. Prior to 2.2.25, 3.1.23, and 3.2.8, Rack::Multipart::Parser can retain parsed data in its internal StringScanner buffer when reads end inside or immediately after multipart headers. An unauthenticated attacker can align many small parts with rack.multipart.buffer_size boundaries so the buffer grows with the request despite per-field, header, and preamble limits, causing a worker to exhaust memory. The attack requires only a well-formed multipart body and affects applications that parse multipart requests. This issue is fixed in versions 2.2.25, 3.1.23, and 3.2.8.

Technical severity7.5 highCVSS 3.1 · CNA: GitHub_M
Published2026-11-09Source updated 2026-11-12
Collected2026-11-125 attributed sources

Fixes and workarounds

Fix

rack (rubygems): GitHub reports patched versions 2.2.25. Check the advisory for the affected release branch.

Source: GitHub GHSA-5v64-555j-wjxm

Fix

rack (rubygems): GitHub reports patched versions 3.1.23. Check the advisory for the affected release branch.

Source: GitHub GHSA-5v64-555j-wjxm

Fix

rack (rubygems): GitHub reports patched versions 3.2.8. Check the advisory for the affected release branch.

Source: GitHub GHSA-5v64-555j-wjxm

Fix

rack (RubyGems): OSV reports a fixed version 2.2.25. Check the advisory for supported release branches.

Source: OSV GHSA-5v64-555j-wjxm

Fix

rack (RubyGems): OSV reports a fixed version 3.1.23. Check the advisory for supported release branches.

Source: OSV GHSA-5v64-555j-wjxm

Fix

rack (RubyGems): OSV reports a fixed version 3.2.8. Check the advisory for supported release branches.

Source: OSV GHSA-5v64-555j-wjxm

Affected products and versions

ProductVersionsAuthority
rack
rack 		< 2.2.25 (affected)
>= 3.0, < 3.1.23 (affected)
>= 3.2, < 3.2.8 (affected) 		CNA: GitHub_M
rack

rack
rubygems 		< 2.2.25 (affected, GitHub advisory range) GitHub GHSA-5v64-555j-wjxm
rack

rack
rubygems 		>= 3.0, < 3.1.23 (affected, GitHub advisory range) GitHub GHSA-5v64-555j-wjxm
rack

rack
rubygems 		>= 3.2, < 3.2.8 (affected, GitHub advisory range) GitHub GHSA-5v64-555j-wjxm
rack

rack
RubyGems 		0.1.0 (affected, RubyGems)
0.2.0 (affected, RubyGems)
0.3.0 (affected, RubyGems)
0.4.0 (affected, RubyGems)
0.9.0 (affected, RubyGems)
0.9.1 (affected, RubyGems)
1.0.0 (affected, RubyGems)
1.0.1 (affected, RubyGems)
1.1.0 (affected, RubyGems)
1.1.1 (affected, RubyGems)
1.1.1.pre (affected, RubyGems)
1.1.2 (affected, RubyGems)
1.1.3 (affected, RubyGems)
1.1.4 (affected, RubyGems)
1.1.5 (affected, RubyGems)
1.1.6 (affected, RubyGems)
1.2.0 (affected, RubyGems)
1.2.1 (affected, RubyGems)
1.2.2 (affected, RubyGems)
1.2.3 (affected, RubyGems)
1.2.4 (affected, RubyGems)
1.2.5 (affected, RubyGems)
1.2.6 (affected, RubyGems)
1.2.7 (affected, RubyGems)
1.2.8 (affected, RubyGems)
1.3.0 (affected, RubyGems)
1.3.0.beta (affected, RubyGems)
1.3.0.beta2 (affected, RubyGems)
1.3.1 (affected, RubyGems)
1.3.10 (affected, RubyGems)
1.3.2 (affected, RubyGems)
1.3.3 (affected, RubyGems)
1.3.4 (affected, RubyGems)
1.3.5 (affected, RubyGems)
1.3.6 (affected, RubyGems)
1.3.7 (affected, RubyGems)
1.3.8 (affected, RubyGems)
1.3.9 (affected, RubyGems)
1.4.0 (affected, RubyGems)
1.4.1 (affected, RubyGems)
1.4.2 (affected, RubyGems)
1.4.3 (affected, RubyGems)
1.4.4 (affected, RubyGems)
1.4.5 (affected, RubyGems)
1.4.6 (affected, RubyGems)
1.4.7 (affected, RubyGems)
1.5.0 (affected, RubyGems)
1.5.0.beta.1 (affected, RubyGems)
1.5.0.beta.2 (affected, RubyGems)
1.5.1 (affected, RubyGems)
1.5.2 (affected, RubyGems)
1.5.3 (affected, RubyGems)
1.5.4 (affected, RubyGems)
1.5.5 (affected, RubyGems)
1.6.0 (affected, RubyGems)
1.6.0.beta (affected, RubyGems)
1.6.0.beta2 (affected, RubyGems)
1.6.1 (affected, RubyGems)
1.6.10 (affected, RubyGems)
1.6.11 (affected, RubyGems)
1.6.12 (affected, RubyGems)
1.6.13 (affected, RubyGems)
1.6.2 (affected, RubyGems)
1.6.3 (affected, RubyGems)
1.6.4 (affected, RubyGems)
1.6.5 (affected, RubyGems)
1.6.6 (affected, RubyGems)
1.6.7 (affected, RubyGems)
1.6.8 (affected, RubyGems)
1.6.9 (affected, RubyGems)
2.0.0.alpha (affected, RubyGems)
2.0.0.rc1 (affected, RubyGems)
2.0.1 (affected, RubyGems)
2.0.2 (affected, RubyGems)
2.0.3 (affected, RubyGems)
2.0.4 (affected, RubyGems)
2.0.5 (affected, RubyGems)
2.0.6 (affected, RubyGems)
2.0.7 (affected, RubyGems)
2.0.8 (affected, RubyGems)
2.0.9 (affected, RubyGems)
2.0.9.1 (affected, RubyGems)
2.0.9.2 (affected, RubyGems)
2.0.9.3 (affected, RubyGems)
2.0.9.4 (affected, RubyGems)
2.1.0 (affected, RubyGems)
2.1.1 (affected, RubyGems)
2.1.2 (affected, RubyGems)
2.1.3 (affected, RubyGems)
2.1.4 (affected, RubyGems)
2.1.4.1 (affected, RubyGems)
2.1.4.2 (affected, RubyGems)
2.1.4.3 (affected, RubyGems)
2.1.4.4 (affected, RubyGems)
2.2.0 (affected, RubyGems)
2.2.1 (affected, RubyGems)
2.2.10 (affected, RubyGems)
2.2.11 (affected, RubyGems)
2.2.12 (affected, RubyGems)
2.2.13 (affected, RubyGems)
2.2.14 (affected, RubyGems)
2.2.15 (affected, RubyGems)
2.2.16 (affected, RubyGems)
2.2.17 (affected, RubyGems)
2.2.18 (affected, RubyGems)
2.2.19 (affected, RubyGems)
2.2.2 (affected, RubyGems)
2.2.20 (affected, RubyGems)
2.2.21 (affected, RubyGems)
2.2.22 (affected, RubyGems)
2.2.23 (affected, RubyGems)
2.2.24 (affected, RubyGems)
2.2.3 (affected, RubyGems)
2.2.3.1 (affected, RubyGems)
2.2.4 (affected, RubyGems)
2.2.5 (affected, RubyGems)
2.2.6 (affected, RubyGems)
2.2.6.1 (affected, RubyGems)
2.2.6.2 (affected, RubyGems)
2.2.6.3 (affected, RubyGems)
2.2.6.4 (affected, RubyGems)
2.2.7 (affected, RubyGems)
2.2.8 (affected, RubyGems)
2.2.8.1 (affected, RubyGems)
2.2.9 (affected, RubyGems)
Ecosystem version events: introduced 0; fixed 2.2.25
Source events (ECOSYSTEM) 
[
  {
    "introduced": "0"
  },
  {
    "fixed": "2.2.25"
  }
]

Other versions: unaffected 		OSV GHSA-5v64-555j-wjxm
rack

rack
RubyGems 		3.0.0 (affected, RubyGems)
3.0.1 (affected, RubyGems)
3.0.10 (affected, RubyGems)
3.0.11 (affected, RubyGems)
3.0.12 (affected, RubyGems)
3.0.13 (affected, RubyGems)
3.0.14 (affected, RubyGems)
3.0.15 (affected, RubyGems)
3.0.16 (affected, RubyGems)
3.0.17 (affected, RubyGems)
3.0.18 (affected, RubyGems)
3.0.2 (affected, RubyGems)
3.0.3 (affected, RubyGems)
3.0.4 (affected, RubyGems)
3.0.4.1 (affected, RubyGems)
3.0.4.2 (affected, RubyGems)
3.0.5 (affected, RubyGems)
3.0.6 (affected, RubyGems)
3.0.6.1 (affected, RubyGems)
3.0.7 (affected, RubyGems)
3.0.8 (affected, RubyGems)
3.0.9 (affected, RubyGems)
3.0.9.1 (affected, RubyGems)
3.1.0 (affected, RubyGems)
3.1.1 (affected, RubyGems)
3.1.10 (affected, RubyGems)
3.1.11 (affected, RubyGems)
3.1.12 (affected, RubyGems)
3.1.13 (affected, RubyGems)
3.1.14 (affected, RubyGems)
3.1.15 (affected, RubyGems)
3.1.16 (affected, RubyGems)
3.1.17 (affected, RubyGems)
3.1.18 (affected, RubyGems)
3.1.19 (affected, RubyGems)
3.1.2 (affected, RubyGems)
3.1.20 (affected, RubyGems)
3.1.21 (affected, RubyGems)
3.1.22 (affected, RubyGems)
3.1.3 (affected, RubyGems)
3.1.4 (affected, RubyGems)
3.1.5 (affected, RubyGems)
3.1.6 (affected, RubyGems)
3.1.7 (affected, RubyGems)
3.1.8 (affected, RubyGems)
3.1.9 (affected, RubyGems)
Ecosystem version events: introduced 3.0.0; fixed 3.1.23
Source events (ECOSYSTEM) 
[
  {
    "introduced": "3.0.0"
  },
  {
    "fixed": "3.1.23"
  }
]

Other versions: unaffected 		OSV GHSA-5v64-555j-wjxm
rack

rack
RubyGems 		3.2.0 (affected, RubyGems)
3.2.1 (affected, RubyGems)
3.2.2 (affected, RubyGems)
3.2.3 (affected, RubyGems)
3.2.4 (affected, RubyGems)
3.2.5 (affected, RubyGems)
3.2.6 (affected, RubyGems)
3.2.7 (affected, RubyGems)
Ecosystem version events: introduced 3.2.0; fixed 3.2.8
Source events (ECOSYSTEM) 
[
  {
    "introduced": "3.2.0"
  },
  {
    "fixed": "3.2.8"
  }
]

Other versions: unaffected 		OSV GHSA-5v64-555j-wjxm

Version ranges are source assertions. Check the vendor advisory and your installed configuration before determining exposure.

CVSS assessments

Version / scoreVectorAuthority
3.1 / 7.5
high		 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:HCNA: GitHub_M
3.1 / 7.5
high		 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:HNVD: [email protected]

Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

References

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