urllib3: HTTPResponse.stream()/read_chunked() buffers an unbounded chunk-size line into memory (CVE-2026-97689) | HOL Guard CVE

High · CVSS 8.9CVE-2026-97689

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

Answer in brief

CVE-2026-97689 records a High severity (CVSS 8.9) vulnerability in urllib3: HTTPResponse.stream()/read_chunked() buffers an unbounded chunk-size line into memory. The current sources do not mark it as known exploited. The current feed maps urllib3/urllib3 (generic). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Sep 29, 2026Updated Sep 29, 2026Source checked Sep 29, 2026First seen by HOL Sep 29, 2026Material review Sep 29, 2026

Upstream Advisory

Key facts

Risk: High · CVSS 8.9
Exploitation: Not marked as known exploited
Affected software: 1 mapped package or product
Fix availability: Available

Why this deserves its current priority

CVSS is 8.9. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps urllib3/urllib3 (generic). Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
urllib3/urllib3generic	>=1.10.3 <2.8.0	2.8.0

Recommended response

Check inventory. Check lockfiles and deployed manifests for urllib3/urllib3.
Review the reported fix. Update urllib3/urllib3 to 2.8.0 if you use the affected versions. Test the change in a non-production environment first.

Evidence timeline and material changes

Published upstream
Sep 29, 2026
Evidence: source:cvelist:source_dates:source-dates:record
Source modified
Sep 29, 2026
Evidence: source:cvelist:source_dates:source-dates:record
First seen by HOL
Sep 29, 2026

Sources and claim methodology

Upstream source description

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.

Quoted source text, attributed separately from HOL analysis.