Vulnerability in urllib3 (CVE-2026-97689)
Summary
Vulnerability in urllib3 (CVE-2026-97689). Risk of unauthorized operations or information disclosure. Mitigation: upgrade to 2.8.0 or later.
Original description
The description as published by the source.
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()](https://urllib3.readthedocs.io/en/stable/reference/urllib3.re…
Source: NIST National Vulnerability Database NVD GitHub Advisory
Auto-generated summary
Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.
A vulnerability tracked as CVE-2026-97689 has been found in urllib3.
Risk of unauthorized operations or information disclosure. CVSS score: 7.5/10.
What to do: upgrade urllib3 to 2.8.0 or later.
If unsure, ask your IT team or search "urllib3 CVE-2026-97689" on the vendor's site.
CVE-2026-97689 (urllib3) — CWE-770 / CVSS v3 7.5
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Patched: 2.8.0 — apply immediately
Workaround: consider reading the response at once using the [read()](https://urllib3.
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.
A vulnerability (CWE-770) exists in urllib3.
Check the vendor advisory for the affected versions of urllib3.
Severity: High (CVSS 7.5/10). Risk of unauthorized operations or information disclosure.
Update to 2.8.0.
Workaround: consider reading the response at once using the [read()](https://urllib3.
Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Run grep -r 'urllib3' . against your dependency files (package-lock.json, requirements.txt, go.sum) to find affected services.
Response actions
Concrete steps and command examples for SOC/SRE teams to execute in order
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1Identify exposure identify
grep -r 'urllib3' . | grep -v node_modulesリポジトリと本番環境の依存ファイル (package-lock.json / requirements.txt / go.sum / Gemfile.lock 等) で
urllib3を grep し、稼働しているサービス・バージョンを把握する。 -
2Apply temporary workaround mitigate
consider reading the response at once using the [read()](https://urllib3.パッチが適用されるまでの応急処置として、consider reading the response at once using the [read()](https://urllib3. を実施。回避策の副作用 (機能低下) を確認した上で。
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3Apply patch patch
Upgrade urllib3 to 2.8.0ステージング環境で 2.8.0 に上げて回帰テスト → 本番反映。回帰テストはアプリの主要ハッピーパスを含めること。
-
4Post-deployment verification verify
Confirm patched version is live in productionパッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。
Affected packages
Fix status by distribution
Fixed packages published by each distribution for this CVE
- Debian DEBIAN-CVE-2026-97689 python-urllib3
- Ubuntu UBUNTU-CVE-2026-97689 python-pip
References
- advisory nvd.nist.gov
- advisory github.com
- package github.com
- package pypi.org
- web github.com
- web github.com
- web github.com