# CVE-2026-125108: Rack is a modular Ruby web server interface. Prior to 2.2.25, 3.1.23, and 3.2.8…

Source: https://junglewise.ai/threats/cve-2026-125108-rack-multipart-boundary-ambiguity-guard-in-rack-multipart-parser  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-11-09  
License: CC BY 4.0 with a link back

CVE-2026-125108 · Severity: low · CVSS 3.7 · Published 2026-11-09

Rack is a modular Ruby web server interface. Prior to 2.2.25, 3.1.23, and 3.2.8, Rack::Multipart::Parser.parse_boundary can skip a leading empty or quoted boundary parameter in a multipart Content-Type header and accept a later parameter. Rack can therefore parse a request body with a boundary that a conforming intermediary would not derive, allowing form fields or file uploads to reach an application without the intended proxy or web application firewall inspection. This issue is fixed in versions 2.2.25, 3.1.23, and 3.2.8.

Technologies: [rack (RubyGems)](https://junglewise.ai/threats/technologies/rack). Vendors: [RubyGems](https://junglewise.ai/threats/vendors/rubygems).

## Quick answers

**Is CVE-2026-125108 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-125108 being exploited in the wild.

**How severe is CVE-2026-125108?** Low severity, with a CVSS score of 3.7, published 9 November 2026.

**Which products and versions are affected?** rack (RubyGems) < 2.2.25, ECOSYSTEM:introduced=0,fixed=2.2.25.

**Is there a fix for CVE-2026-125108?** Yes. rack (RubyGems): upgrade to 2.2.25 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**Am I affected by CVE-2026-125108?** Check whether you run rack (RubyGems) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- rack (RubyGems): upgrade to 2.2.25 or later

  ```sh
  bundle update rack
  ```


## Affected products

- rack (RubyGems) < 2.2.25, ECOSYSTEM:introduced=0,fixed=2.2.25

## Identifiers

- CVE-2026-125108
- GHSA-p8x9-v4hv-2w4g

## Related threats

- [Rack multipart parser denial of service via unbounded scan buffer growth](https://junglewise.ai/threats/cve-2026-125111-rack-multipart-parsing-allows-dos-via-unbounded-scan-buffer)
- [Rack::Static header_rules bypass via dot-segment normalization mismatch](https://junglewise.ai/threats/cve-2026-125110-rack-rack-static-header-rules-bypass-via-dot-segment)
- [Rack host validation bypass via HTTP headers](https://junglewise.ai/threats/cve-2026-125109-rack-is-a-modular-ruby-web-server-interface-from-3-0-until-3-1)
- [Rack Rack::Request host allowlist bypass via Host header poisoning](https://junglewise.ai/threats/cve-2026-34835-rack-rack-request-host-allowlist-bypass-via-host-header-poisoning)
- [Rack algorithmic complexity denial of service in Multipart Parser](https://junglewise.ai/threats/cve-2026-34827-rack-algorithmic-complexity-denial-of-service-in-multipart-parser)