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

Quick assessment

Affected
urllib3 urllib3
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

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 le

CVSS 8.9 · High
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I. Basic Information for CVE-2026-97689

Vulnerability Information

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Vulnerability Title
urllib3: HTTPResponse.stream()/read_chunked() buffers an unbounded chunk-size line into memory
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
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
Source: CVE Program / CVE List V5
Vulnerability Type
不加限制或调节的资源分配
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
urllib3 urllib3 >= 1.10.3, < 2.8.0 -

II. Public POCs for CVE-2026-97689

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III. Intelligence Information for CVE-2026-97689

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Other References for CVE-2026-97689 (3)

Same Patch Batch · urllib3 · 2026-09-29 · 3 CVEs total

CVE-2026-97687 7.6 HIGH urllib3: HTTPS proxy TLS configuration may be ignored or overridden
CVE-2026-97688 6.9 MEDIUM urllib3: Chunked Deflate streaming can enter an infinite loop

IV. Related Vulnerabilities

Same product: urllib3
Same vendor: urllib3
Same weakness: CWE-770

V. Comments for CVE-2026-97689

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