GHSA-vxq7-64xx-v4gw

Source

https://github.com/advisories/GHSA-vxq7-64xx-v4gw

Import Source

https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/09/GHSA-vxq7-64xx-v4gw/GHSA-vxq7-64xx-v4gw.json

JSON Data

https://api.osv.dev/v1/vulns/GHSA-vxq7-64xx-v4gw

Aliases

CVE-2026-97689

Downstream

ECHO-3e87-5898-34ca

Published

2026-09-30T14:46:18Z

Modified

2026-09-30T15:00:05Z

Severity

8.9 (High) CVSS_V4 - 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 CVSS Calculator

Summary

urllib3: HTTPResponse.stream()/read_chunked() buffers an unbounded chunk-size line into memory

Details

Impact

urllib3's streaming API is designed for efficiently handling large HTTP responses by reading the content in chunks, rather than loading the entire response body into memory at once. When decoding a chunked-transfer-encoded response, this API reads each chunk's size field by buffering until it sees \n or EOF.

A malicious HTTP server can return Transfer-Encoding: chunked and then send a very long run of bytes without any newline, causing the streaming client to buffer that entire run before urllib3 can reject the chunk size as invalid and allocate more memory than intended.

To fix the issue, we'll reject chunk-size fields larger than 65536 bytes, as already done in the non-streaming case, which is currently handled by the Python standard library. Note that this only applies to reading the chunk-size field, not the chunk data, which is already handled correctly. Thus, there shouldn't be any impact for non-malicious servers.

Affected usages

Applications and libraries using urllib3 versions earlier than 2.8.0 may be affected when streaming a chunked response from untrusted sources. Specifically, this affects the read_chunked() and stream() methods of the HTTPResponse object.

This also affects requests streaming API, which uses urllib3 under the hood.

Remediation

Upgrade to urllib3 version 2.8.0 or later, where chunk-size fields larger than 65536 will be rejected. If upgrading is not immediately possible, consider reading the response at once using the read() method.

Database specific

{
    "cwe_ids":  [
        "CWE-770"
    ],
    "github_reviewed":  true,
    "github_reviewed_at":  "2026-09-30T14:46:18Z",
    "nvd_published_at":  "2026-09-29T16:17:18Z",
    "severity":  "HIGH"
}

References

Affected packages

PyPI / urllib3

Package

Name: urllib3; View open source insights on deps.dev
Purl: pkg:pypi/urllib3

Affected ranges

Type: ECOSYSTEM
Events: Introduced

1.10.3

Fixed

2.8.0

Affected versions

1.*

1.10.3

1.10.4

1.11

1.12

1.13

1.13.1

1.14

1.15

1.15.1

1.16

1.17

1.18

1.18.1

1.19

1.19.1

1.20

1.21

1.21.1

1.22

1.23

1.24

1.24.1

1.24.2

1.24.3

1.25

1.25.1

1.25.2

1.25.3

1.25.4

1.25.5

1.25.6

1.25.7

1.25.8

1.25.9

1.25.10

1.25.11

1.26.0

1.26.1

1.26.2

1.26.3

1.26.4

1.26.5

1.26.6

1.26.7

1.26.8

1.26.9

1.26.10

1.26.11

1.26.12

1.26.13

1.26.14

1.26.15

1.26.16

1.26.17

1.26.18

1.26.19

1.26.20

2.*

2.0.0a1

2.0.0a2

2.0.0a3

2.0.0a4

2.0.0

2.0.1

2.0.2

2.0.3

2.0.4

2.0.5

2.0.6

2.0.7

2.1.0

2.2.0

2.2.1

2.2.2

2.2.3

2.3.0

2.4.0

2.5.0

2.6.0

2.6.1

2.6.2

2.6.3

2.7.0

Database specific

source

"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/09/GHSA-vxq7-64xx-v4gw/GHSA-vxq7-64xx-v4gw.json"