Description
urllib3 is an HTTP client library for Python. From 2.6.0 to before 2.7.0, urllib3 could decompress the whole response instead of the requested portion (1) during the second HTTPResponse.read(amt=N) call when the response was decompressed using the official Brotli library or (2) when HTTPResponse.drain_conn() was called after the response had been read and decompressed partially (compression algorithm did not matter here). These issues could cause urllib3 to fully decode a small amount of highly compressed data in a single operation. This could result in excessive resource consumption (high CPU usage and massive memory allocation for the decompressed data) on the client side. This vulnerability is fixed in 2.7.0.
Affected products
python: urllib3
References10
- github.com/urllib3/urllib3/security/advisories/GHSA-mf9v-mfxr-j… MitigationVendor Advisory
- access.redhat.com/errata/RHSA-2026:15862
- access.redhat.com/errata/RHSA-2026:20338
- access.redhat.com/errata/RHSA-2026:22934
- access.redhat.com/errata/RHSA-2026:24000
- access.redhat.com/errata/RHSA-2026:24009
- access.redhat.com/errata/RHSA-2026:24014
- access.redhat.com/errata/RHSA-2026:24069
- access.redhat.com/errata/RHSA-2026:24374
- access.redhat.com/errata/RHSA-2026:24476
Metrics
- CVSS 3.1
-
7.5
HIGH
Score source: NVD
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H - CVSS 4.0
-
8.9
HIGH
Score source: CNA
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 - EPSS — exploit probability
- 1% percentile: 53 · as of 14 November 2026
- CWE
- CWE-409
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