CVE-2026-97687 · GHSA-8988-9cw3-xx77
urllib3: HTTPS proxy TLS configuration may be ignored or overridden
- Risk score
- 66/100
- CVSS
- 8.1 v3.1
- Exploit chance (30 days)
- 0.2%
- Published
- 29 Sep 2026
Open in the live forecast Today's forecast
What to know
- What it is
- urllib3 is an HTTP client library for Python. From 1.26.0 until 2.8.0, the proxy_ssl_context, proxy_assert_hostname, proxy_assert_fingerprint, ssl_context, cert_reqs, verify_mode, use_forwarding_for_https=True, and CERT_NONE configuration paths fail to remain separated because target-server TLS settings are incorrectl…
- Affected
- urllib3 (pip) >= 1.26.0, < 2.8.0
- Fix
- Upgrade urllib3 to 2.8.0 or later.
- Exploitation
- No known exploitation
Story map
At a glance
urllib3: Amber, patch this week. urllib3 is an HTTP client library for Python. From 1.26.0 until 2.8.0, the proxy_ssl_context, proxy_assert_hostname, proxy_assert_fingerprint, ssl_context, cert_reqs, verify_mode, use_forwarding_for_https=True, and CERT_NONE configuration paths fail to remain separated because target-server TLS settings are incorrectl…
The flaws
- CVE-2026-97687: HTTPS proxy TLS configuration may be ignored or overridden (CVSS 8.1 · EPSS 0%)
- CVE-2026-97689: HTTPResponse.stream()/read_chunked() buffers an unbounded chunk-size line into memory (CVSS 7.5 · EPSS 0%)
- CVE-2026-97688: Chunked Deflate streaming can enter an infinite loop (CVSS 5.3 · EPSS 0%)
The fix
Upgrade urllib3: 2.8.0 or later on your release line
Who is exposed: urllib3 (pip) >= 1.26.0, < 2.8.0
Where it stands
- No known exploitation
Connects to
- Same weakness: CWE-295 (CWE-295). 82 other warnings in 30 days
Why it is Amber
- CVSS 8.1 high
- Remotely exploitable without logging in
- On your watchlist: python, PyPI
Affected packages
| Package | Ecosystem | Vulnerable | Fixed in |
|---|---|---|---|
| urllib3 | pip | >= 1.26.0, < 2.8.0 | 2.8.0 |
References
- https://github.com/advisories/GHSA-8988-9cw3-xx77
- https://github.com/urllib3/urllib3/security/advisories/GHSA-8988-9cw3-xx77
- https://nvd.nist.gov/vuln/detail/CVE-2026-97687
- https://github.com/urllib3/urllib3/pull/5093
- https://github.com/urllib3/urllib3/commit/07408cec79d1856d81bb42c74a904a24fdb9e465
- https://github.com/urllib3/urllib3/commit/b6447295fff7b38fdffc67e0df9712d60cef3cc3
- https://github.com/urllib3/urllib3/releases/tag/2.8.0
- https://github.com/advisories/GHSA-8988-9cw3-xx77
Original description
urllib3 is an HTTP client library for Python. From 1.26.0 until 2.8.0, the proxy_ssl_context, proxy_assert_hostname, proxy_assert_fingerprint, ssl_context, cert_reqs, verify_mode, use_forwarding_for_https=True, and CERT_NONE configuration paths fail to remain separated because target-server TLS settings are incorrectly applied to the HTTPS proxy connection. The trigger is that an application uses an HTTPS proxy and configures target-server TLS settings that must remain separate from the proxy TLS handshake, including HTTPS forwarding with target-specific identity or credentials. Applying cert_reqs=CERT_NONE can overwrite proxy_ssl_context.verify_mode in place, and the mutation persists so later connections reusing the same context may connect to the HTTPS proxy without certificate verification. The attack mechanism is that an attacker intercepts and impersonates the HTTPS proxy after the effective proxy policy accepts the attacker's certificate. The impact is that the attacker can observe or modify forwarded traffic or receive a target TLS client certificate, while CONNECT tunneling still preserves the separate end-to-end target TLS connection. This issue is fixed in version 2.8.0.
Last activity 29 Sep 2026. Patch Forecast updates every hour.