Vulnerability details
CVE-2026-97689
urllib3 urllib3
urllib3: HTTPResponse.stream()/read_chunked() buffers an unbounded chunk-size line into memory
CVSS 4.0
8.9High
Official 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.
CVSS scores
| Score | Version | Source | Vector |
|---|---|---|---|
| 8.9High | 4.0 | CVEProject cvelistV5 (CNA) (GitHub_M) | 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 |
Affected products
| Vendor | Product | Versions | Source |
|---|---|---|---|
| urllib3 | urllib3 | >= 1.10.3, < 2.8.0 | CVEProject cvelistV5 (CNA) |
References and advisories
3- https://github.com/urllib3/urllib3/security/advisories/GHSA-vxq7-64xx-v4gw x_refsource_CONFIRM
- https://github.com/urllib3/urllib3/commit/cd770b059b543be29298ea5c52afb0b1b090f5ed x_refsource_MISC
- https://github.com/urllib3/urllib3/releases/tag/2.8.0 x_refsource_MISC
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Details
- Published
- 2026-09-29
- Last updated
- 2026-09-29
- State
- Published
- Assigner (CNA)
- GitHub_M
Exploit prediction (EPSS)
0.33%
Probability of exploitation in 30 days
27%
Percentile (among all CVEs)
SSVC assessment (CISA)
- Automatable
- No
- Exploitation
- None
- Technical impact
- Partial
Weaknesses (CWE)
- CWE-770Allocation of Resources Without Limits or Throttling