CVE-2026-32239: Cap'n Proto has an integer overflow in KJ-HTTP
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.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
debian/capnprototo a version that resolves this vulnerability.Fixed in 1.4.0-3 - Upgrade
Upgrade
Cap'n Proto (KJ-HTTP)to a version that resolves this vulnerability.Fixed in 1.4.0
Event History
Frequently Asked Questions
What is the severity of CVE-2026-32239?
CVE-2026-32239 has a high severity due to its potential to cause an integer overflow leading to unexpected behavior in applications using affected versions.
How do I fix CVE-2026-32239?
To fix CVE-2026-32239, upgrade Cap'n Proto to version 1.4.0 or later, where the integer overflow issue has been addressed.
What software is affected by CVE-2026-32239?
CVE-2026-32239 affects Cap'n Proto versions prior to 1.4.0, specifically the handling of negative Content-Length values.
What could be the impact of exploiting CVE-2026-32239?
Exploiting CVE-2026-32239 could lead to denial of service or execution of arbitrary code due to mishandling of HTTP request lengths.
Is there a workaround for CVE-2026-32239 if I cannot immediately update?
As a temporary workaround for CVE-2026-32239, avoid processing negative Content-Length values until an upgrade can be applied.