Bug 2398167 (CVE-2025-59830)

Summary: CVE-2025-59830 rubygem-rack: Rack QueryParser has an unsafe default allowing params_limit bypass via semicolon-separated parameters
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedCC: akostadi, amasferr, anthomas, cbartlet, crizzo, dmayorov, eglynn, ehelms, ggainey, jcantril, jjoyce, jlledo, jschluet, juwatts, jvasik, kaycoth, lhh, lsvaty, mburns, mgarciac, mhulan, mkudlej, mmakovy, nmoumoul, osousa, pcreech, pgrist, rblanco, rchan, rojacob, smallamp, tjochec, tmalecek, vmugicag
Target Milestone: ---Keywords: Security
Target Release: ---   
Hardware: All   
OS: Linux   
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An unsafe default behavior in Rack::QueryParser allows bypass of the params_limit parameter count restriction when query string parameters are delimited by semicolons (;) rather than ampersands (&). The parser counts only & when enforcing the limit, while still splitting on both & and ;. As a result, an attacker can supply a crafted HTTP query using ; delimiters to exceed the intended parameter count, potentially causing performance degradation or exhaustion of resources (denial of service).
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
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Bug Depends On: 2402984, 2402985, 2402986, 2402987, 2402988, 2402982, 2402983    
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Description OSIDB Bzimport 2025-09-25 15:02:05 UTC 
Rack is a modular Ruby web server interface. Prior to version 2.2.18, Rack::QueryParser enforces its params_limit only for parameters separated by &, while still splitting on both & and ;. As a result, attackers could use ; separators to bypass the parameter count limit and submit more parameters than intended. Applications or middleware that directly invoke Rack::QueryParser with its default configuration (no explicit delimiter) could be exposed to increased CPU and memory consumption. This can be abused as a limited denial-of-service vector. This issue has been patched in version 2.2.18.