Bug 2447106 (CVE-2026-32239)

Summary: CVE-2026-32239 capnproto: Cap'n Proto has an integer overflow in KJ-HTTP
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: unspecifiedKeywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in the KJ-HTTP component of Cap’n Proto. When processing HTTP messages, a negative Content-Length value could be implicitly converted to an unsigned integer, resulting in an extremely large length value. An attacker could exploit this behavior by sending specially crafted HTTP messages containing negative Content-Length values. This may lead to inconsistent interpretation of HTTP message boundaries and could theoretically enable HTTP request or response smuggling scenarios in applications that rely on Cap’n Proto’s HTTP implementation.
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Bug Depends On: 2447306, 2447307    
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Description OSIDB Bzimport 2026-03-12 20:01:26 UTC
Cap'n Proto is a data interchange format and capability-based RPC system. Prior to 1.4.0, a negative Content-Length value was converted to unsigned, treating it as an impossibly large length instead. In theory, this bug could enable HTTP request/response smuggling. This vulnerability is fixed in 1.4.0.