CVE-2026-21441: fallo de gravedad alta en urllib3
urllib3 vulnerable to decompression-bomb safeguard bypass when following HTTP redirects (streaming API)
Publicada el · Actualizada el
Aviso por correo cuando entre en el KEV, tenga PoC pública o suba de nota.
21Vexday Risk Score
Sin señal de explotación. Ningún artefacto público de explotación conocido hasta ahora.
ssvc Trackcvss 8.9epss 2.9%
urllib3 is an HTTP client library for Python. urllib3's streaming API is designed for the efficient handling of large HTTP responses by reading the content in chunks, rather than loading the entire response body into memory at once. urllib3 can perform decoding or decompression based on the HTTP `Content-Encoding` header (e.g., `gzip`, `deflate`, `br`, or `zstd`). When using the streaming API, the library decompresses only the necessary bytes, enabling partial content consumption. Starting in version 1.22 and prior to version 2.6.3, for HTTP redirect responses, the library would read the entire response body to drain the connection and decompress the content unnecessarily. This decompression occurred even before any read methods were called, and configured read limits did not restrict the amount of decompressed data. As a result, there was no safeguard against decompression bombs. A malicious server could exploit this to trigger excessive resource consumption on the client. Applications and libraries are affected when they stream content from untrusted sources by setting `preload_content=False` when they do not disable redirects. Users should upgrade to at least urllib3 v2.6.3, in which the library does not decode content of redirect responses when `preload_content=False`. If upgrading is not immediately possible, disable redirects by setting `redirect=False` for requests to untrusted source.
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:H
Productos afectados
urllib3 · urllib3CVEs relacionadas — urllib3
En el mismo producto, de las más peligrosas a las menos.
CVE-2023-43804MEDIUM`Cookie` HTTP header isn't stripped on cross-origin redirectsEPSS 1.4%CVE-2024-37891MEDIUMProxy-Authorization request header isn't stripped during cross-origin redirects in urllib3EPSS 1.1%CVE-2025-66471HIGHurllib3 Streaming API improperly handles highly compressed dataEPSS 0.7%CVE-2025-66418HIGHurllib3 allows an unbounded number of links in the decompression chainEPSS 0.7%CVE-2026-44432HIGHurllib3: Decompression-bomb safeguards bypassed in parts of the streaming APIEPSS 0.7%CVE-2025-50182MEDIUMurllib3 does not control redirects in browsers and Node.jsEPSS 0.6%
Referencias
https://access.redhat.com/errata/RHSA-2026:0981https://access.redhat.com/errata/RHSA-2026:0990https://access.redhat.com/errata/RHSA-2026:10184https://access.redhat.com/errata/RHSA-2026:1038https://access.redhat.com/errata/RHSA-2026:1041https://access.redhat.com/errata/RHSA-2026:1042https://access.redhat.com/errata/RHSA-2026:1086https://access.redhat.com/errata/RHSA-2026:1087https://access.redhat.com/errata/RHSA-2026:1088https://access.redhat.com/errata/RHSA-2026:1089https://access.redhat.com/errata/RHSA-2026:1166https://access.redhat.com/errata/RHSA-2026:1168