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fkie_cve-2026-97689

2026-09-30T22:00:46.697780+00:00

urllib3 is an HTTP client library for Python. From 1.10.3 until 2.8.0, the HTTPResponse.read_chunked and HTTPResponse.stream methods can allocate unbounded memory because the streaming chunk parser buffers the chunk-size field until newline or EOF without a length bound. The trigger is that a malicious server returns Transfer-Encoding: chunked followed by a very long run of bytes without a newline. The attack mechanism is that a malicious HTTP server sends a very long unterminated chunk-size line. The impact is that unbounded memory allocation can exhaust the client process. This issue is fixed in version 2.8.0.

GHSA-vxq7-64xx-v4gw — urllib3: HTTPResponse.stream()/read_chunked() buffers an unbounded chunk-size line into memory

2026-09-30T22:00:46.697893+00:00

Affected: PyPI: urllib3

## Impact

urllib3's [streaming API](https://urllib3.readthedocs.io/en/2.7.0/advanced-usage.html#streaming-and-i-o) 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](https://httpwg.org/specs/rfc9112.html#chunked.encoding), 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()](https://urllib3.readthedocs.io/en/stable/reference/urllib3.response.html#urllib3.response.BaseHTTPResponse.read_chunked) and [stream()](https://urllib3.readthedocs.io/en/stable/reference/urllib3.r…

RHSA-2026:69612 — Red Hat Security Advisory: Red Hat Hardened Images RPMs bug fix and enhancement update

2026-09-30T22:00:46.697994+00:00

urllib3: urllib3: Traffic interception via HTTPS proxy TLS configuration override urllib3: urllib3: Denial of Service via infinite loop during chunked Deflate decoding urllib3: urllib3: Denial of Service via unbounded memory allocation in chunk parser