CVE catalog
CVE-2026-21441
urllib3 vulnerability
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.
- Severity
- High · CVSS 8.9
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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X - Published
- Source
- [NVD] · [CVE record]
- EPSS
- 2.92% · Oct 27, 2026
Projects and upstream resources
Reported versions and fixes
Each observation applies to its named package, distribution, and release. Distribution backports can fix a vulnerability while retaining an older upstream version number.
Version impact has not been established. The original provider fields are retained below.
Provider details and historical evidence
Original provider fields
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}OpenFactory catalog packages
Matching against OpenFactory catalog package versions is in progress.
[Debian 12 (Bookworm)]
- [python3-urllib3]Unknown
Source package: [python-urllib3]
Details (4)
1.26.12-1+deb12u4· all · bookwormFixed · Fixed:
1.26.12-1+deb12u3usn · python-urllib3 · debian · bookworm; usn · python-urllib3 · debian · 12
1.26.12-1+deb12u4· all · bookwormFixed · Fixed:
1.26.12-1+deb12u3usn · python-urllib3 · debian · bookworm; usn · python-urllib3 · debian · 12
1.26.12-1+deb12u4· all · bookworm-securityFixed · Fixed:
1.26.12-1+deb12u3usn · python-urllib3 · debian · bookworm; usn · python-urllib3 · debian · 12
1.26.12-1+deb12u4· all · bookworm-securityFixed · Fixed:
1.26.12-1+deb12u3usn · python-urllib3 · debian · bookworm; usn · python-urllib3 · debian · 12
[Debian 13 (Trixie)]
- [python3-urllib3]Unknown
Source package: [python-urllib3]
Details (4)
2.3.0-3+deb13u2· all · trixieFixed · Fixed:
2.3.0-3+deb13u1usn · python-urllib3 · debian · 13
2.3.0-3+deb13u2· all · trixieFixed · Fixed:
2.3.0-3+deb13u1usn · python-urllib3 · debian · 13
2.3.0-3+deb13u2· all · trixie-securityFixed · Fixed:
2.3.0-3+deb13u1usn · python-urllib3 · debian · 13
2.3.0-3+deb13u2· all · trixie-securityFixed · Fixed:
2.3.0-3+deb13u1usn · python-urllib3 · debian · 13
[openSUSE Tumbleweed]
- [python313-urllib3]Unknown
Source package: [python-urllib3]
Details (1)
2.7.0-2.3· noarch · tumbleweedUnknown · Fixed:
2.6.3-1.1Version impact unknown
usn · python-urllib3 · opensuse · tumbleweed
- [python314-urllib3]Unknown
Source package: [python-urllib3]
Details (1)
2.7.0-2.3· noarch · tumbleweedUnknown · Fixed:
2.6.3-1.1Version impact unknown
usn · python-urllib3 · opensuse · tumbleweed
Observed:
References
- [https://access.redhat.com/errata/RHSA-2026:1942]
- [https://ftp.suse.com/pub/projects/security/csaf/opensuse-su-2026_10049-1.json]
- [https://nvd.nist.gov/vuln/detail/CVE-2026-21441]
- [https://osv.dev/vulnerability/ALPINE-CVE-2026-21441]
- [https://osv.dev/vulnerability/DEBIAN-CVE-2026-21441]
- [https://osv.dev/vulnerability/DLA-4446-1]
- [https://osv.dev/vulnerability/DSA-6102-2]
- [https://osv.dev/vulnerability/GHSA-38jv-5279-wg99]
- [https://osv.dev/vulnerability/SUSE-SU-2026:0255-1]
- [https://osv.dev/vulnerability/SUSE-SU-2026:0255-2]
- [https://osv.dev/vulnerability/SUSE-SU-2026:20131-1]
- [https://osv.dev/vulnerability/SUSE-SU-2026:20157-1]
- [https://osv.dev/vulnerability/SUSE-SU-2026:20270-1]
- [https://osv.dev/vulnerability/SUSE-SU-2026:20364-1]
- [https://osv.dev/vulnerability/USN-7955-1]
- [https://osv.dev/vulnerability/openSUSE-SU-2026:10049-1]
- [https://osv.dev/vulnerability/openSUSE-SU-2026:20088-1]
- [https://security-tracker.debian.org/tracker/CVE-2026-21441]
- [https://ubuntu.com/security/notices/USN-7955-1]
- [https://wid.cert-bund.de/.well-known/csaf/white/2026/wid-sec-w-2026-1194.json]
[CERT-Bund public advisories] · [Debian Security Tracker] · [FIRST EPSS] · [National Vulnerability Database (NVD)] · [OSV Package Vulnerability Database] · [Red Hat security advisories and VEX] · [SUSE security advisories and VEX] · [Ubuntu Security Notices (USN)]