Rack: Multipart boundary ambiguity guard in Rack::Multipart::Parser can be bypassed with a quoted boundary value, allowing WAF bypass
- Exploited
- No known exploitation
- Fix
- Fixed in 2.2.25, 3.1.23, 3.2.8
- Who is exposed
- Not reported
Do first: Upgrade to a fixed version: 2.2.25, 3.1.23, 3.2.8.
- Last modified
- A 0-100 score for how much a CVE matters across the industry: exploitation, exposure, how widely the software is used, severity and whether a fix exists.What do these mean? →
- 21/100 · provisional
- Whether working attack code is public (Exploit-DB, Metasploit, Nuclei or GitHub). Public code makes attacks easier.What do these mean? →
- None on Exploit-DB, Metasploit or GitHub
Summary
Rack, a Ruby web server interface, has a flaw in how its multipart parser handles the boundary value in a Content-Type header, so it can accept a boundary that a proxy or web application firewall would not derive. An attacker can exploit this remotely, without logging in, to get form fields or file uploads past inspection by an intermediary.
Written by anthropic/claude-haiku-5.5 from the sources below. Verify against them.
Read the original description
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.
cve.now Index
- Exploitation?/40Unknown. No CISA SSVC exploitation rating yet
- Exposure17/25No login or user action needed per the CVSS vector, reachable over the network without a login · Unknown: No advisory context yet
- Reach?/20Unknown. No tracked technology or package matched
- Severity3.7/10CVSS 3.7
- No patch0/5No signal
What would change the score
- Would score about 66 if added to CISA KEV
- Would score about 61 if CISA's SSVC rates exploitation active
- Would score about 26 if advisories confirm default setups are exposed
What to do
Upgrade to a fixed version: 2.2.25, 3.1.23, 3.2.8.
Timeline
- CVE published
- First seen by cve.now
Affected versions
- rack rack
fixed in 2.2.25; From 3.0 · fixed in 3.1.23; From 3.2 · fixed in 3.2.8
Evidence 7
- Advisory
- Repository
- Repository
- Repository
- Repository
Show all 7 sourcesShow fewer sources
- Repository
- Repository
Corrections
None so far.
Something wrong on this page? Report an error. Every fix is listed here.
Questions about CVE-2026-125108
Is CVE-2026-125108 being exploited?
It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked.Source: cve.now feed data
Which versions are affected by CVE-2026-125108?
rack: before 2.2.25; from 3.0 before 3.1.23; from 3.2 before 3.2.8.Source: cve.now feed data
How do I fix CVE-2026-125108?
Upgrade to a fixed version: 2.2.25, 3.1.23, 3.2.8.Source: cve.now feed data