Rack is a modular Ruby web server interface. In versions prior to 2.2.19, 3.1.17, and 3.2.2, `Rack::Multipart::Parser` buffers the entire multipart preamble (bytes before the first boundary) in memory without any size limit. A client can send a large preamble followed by a valid boundary, causing significant memory use and potential process termination due to out-of-memory (OOM) conditions. Remote attackers can trigger large transient memory spikes by including a long preamble in multipart/form-data requests. The impact scales with allowed request sizes and concurrency, potentially causing worker crashes or severe slowdown due to garbage collection. Versions 2.2.19, 3.1.17, and 3.2.2 enforce a preamble size limit (e.g., 16 KiB) or discard preamble data entirely. Workarounds include limiting total request body size at the proxy or web server level and monitoring memory and set per-process limits to prevent OOM conditions.
This issue has been addressed in the following products: Red Hat Enterprise Linux 10 Via RHSA-2025:19513 https://access.redhat.com/errata/RHSA-2025:19513
This issue has been addressed in the following products: Red Hat Enterprise Linux 9 Via RHSA-2025:19512 https://access.redhat.com/errata/RHSA-2025:19512
This issue has been addressed in the following products: Red Hat Enterprise Linux 8.8 Update Services for SAP Solutions Red Hat Enterprise Linux 8.8 Telecommunications Update Service Via RHSA-2025:19647 https://access.redhat.com/errata/RHSA-2025:19647
This issue has been addressed in the following products: Red Hat Enterprise Linux 8 Via RHSA-2025:19719 https://access.redhat.com/errata/RHSA-2025:19719
This issue has been addressed in the following products: Red Hat Enterprise Linux 9.2 Update Services for SAP Solutions Via RHSA-2025:19733 https://access.redhat.com/errata/RHSA-2025:19733
This issue has been addressed in the following products: Red Hat Enterprise Linux 8.6 Advanced Mission Critical Update Support Red Hat Enterprise Linux 8.6 Update Services for SAP Solutions Red Hat Enterprise Linux 8.6 Telecommunications Update Service Via RHSA-2025:19734 https://access.redhat.com/errata/RHSA-2025:19734
This issue has been addressed in the following products: Red Hat Enterprise Linux 9.4 Extended Update Support Via RHSA-2025:19736 https://access.redhat.com/errata/RHSA-2025:19736
This issue has been addressed in the following products: Red Hat Enterprise Linux 9.0 Update Services for SAP Solutions Via RHSA-2025:19800 https://access.redhat.com/errata/RHSA-2025:19800
This issue has been addressed in the following products: Red Hat Enterprise Linux 8.4 Advanced Mission Critical Update Support Red Hat Enterprise Linux 8.4 Extended Update Support Long-Life Add-On Via RHSA-2025:19948 https://access.redhat.com/errata/RHSA-2025:19948
This issue has been addressed in the following products: Red Hat Enterprise Linux 9 Via RHSA-2025:20962 https://access.redhat.com/errata/RHSA-2025:20962
This issue has been addressed in the following products: Red Hat Enterprise Linux 10 Via RHSA-2025:21036 https://access.redhat.com/errata/RHSA-2025:21036
This issue has been addressed in the following products: Red Hat Enterprise Linux 7 Extended Lifecycle Support Via RHSA-2025:21696 https://access.redhat.com/errata/RHSA-2025:21696