ALPINE-CVE-2026-21441
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.
ALPINE-CVE-2026-21441
Primary source · Revision 1
Imported from structured advisory data. Source references identify upstream records or fields; verify affected versions and your deployed configuration.
Security context
Source reference: osv:ALPINE-CVE-2026-21441
py3-urllib3
Source reference: /affected/0/package/name
- Affected versions
- Not stated in this record
- Fixed versions
- 1.26.18-r2
Source reference:
/affected/0/ranges - Prerequisites
- Not stated in this record
py3-urllib3
Source reference: /affected/1/package/name
- Affected versions
- Not stated in this record
- Fixed versions
- 1.26.20-r1
Source reference:
/affected/1/ranges - Prerequisites
- Not stated in this record
py3-urllib3
Source reference: /affected/2/package/name
- Affected versions
- Not stated in this record
- Fixed versions
- 1.26.20-r1
Source reference:
/affected/2/ranges - Prerequisites
- Not stated in this record
py3-urllib3
Source reference: /affected/3/package/name
- Affected versions
- Not stated in this record
- Fixed versions
- 2.6.3-r0
Source reference:
/affected/3/ranges - Prerequisites
- Not stated in this record
py3-urllib3
Source reference: /affected/4/package/name
- Affected versions
- Not stated in this record
- Fixed versions
- 2.6.3-r0
Source reference:
/affected/4/ranges - Prerequisites
- Not stated in this record
Structured affected-version data
Original package identities and version rules from this source.
[
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
},
{
"fixed": "1.26.18-r2"
}
]
}
],
"package": {
"name": "py3-urllib3",
"purl": "pkg:apk/alpine/py3-urllib3?arch=source",
"ecosystem": "Alpine:v3.20"
},
"database_specific": {
"source": "https://storage.googleapis.com/cve-osv-conversion/alpine/ALPINE-CVE-2026-21441.json"
},
"ecosystem_specific": {}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
},
{
"fixed": "1.26.20-r1"
}
]
}
],
"package": {
"name": "py3-urllib3",
"purl": "pkg:apk/alpine/py3-urllib3?arch=source",
"ecosystem": "Alpine:v3.21"
},
"database_specific": {
"source": "https://storage.googleapis.com/cve-osv-conversion/alpine/ALPINE-CVE-2026-21441.json"
},
"ecosystem_specific": {}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
},
{
"fixed": "1.26.20-r1"
}
]
}
],
"package": {
"name": "py3-urllib3",
"purl": "pkg:apk/alpine/py3-urllib3?arch=source",
"ecosystem": "Alpine:v3.22"
},
"database_specific": {
"source": "https://storage.googleapis.com/cve-osv-conversion/alpine/ALPINE-CVE-2026-21441.json"
},
"ecosystem_specific": {}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
},
{
"fixed": "2.6.3-r0"
}
]
}
],
"package": {
"name": "py3-urllib3",
"purl": "pkg:apk/alpine/py3-urllib3?arch=source",
"ecosystem": "Alpine:v3.23"
},
"database_specific": {
"source": "https://storage.googleapis.com/cve-osv-conversion/alpine/ALPINE-CVE-2026-21441.json"
},
"ecosystem_specific": {}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
},
{
"fixed": "2.6.3-r0"
}
]
}
],
"package": {
"name": "py3-urllib3",
"purl": "pkg:apk/alpine/py3-urllib3?arch=source",
"ecosystem": "Alpine:v3.24"
},
"database_specific": {
"source": "https://storage.googleapis.com/cve-osv-conversion/alpine/ALPINE-CVE-2026-21441.json"
},
"ecosystem_specific": {}
}
]Publisher severity
No explicit severity was provided.
- Event
- #54157 · Revision 1
- Added to Heist Feed
- Publisher date