CVE-2026-97687 — urllib3: HTTPS proxy TLS configuration may be ignored or overridden
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.
Who exploits it and how urgent it is
A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.
How the score was calculated
- EPSS 0.2% (30-day exploitation probability)+1
- Technical severity (high)+6
The score orders the patch queue; it does not replace your asset context (internet exposure, criticality, compensating controls).
Triage
Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.
CISA SSVC assessment CISA
Three decision points CISA publishes for the CVEs it assesses (SSVC 2.0.3). A stakeholder decision, not a severity score.
Remediation
Fixes and mitigations documented by the sources — linked to the original advisory.
- Documented patch — github.com (NIST National Vulnerability Database)
- Documented patch — github.com (NIST National Vulnerability Database)
- Documented patch — github.com (NIST National Vulnerability Database)
- Pip Urllib3: fixed in version 2.8.0 — github.com (GitHub Security Advisories)
First 24 hours
Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.
- Identify exposed assets running the affected vendor/product/version combinations (Python Urllib3, Urllib3 Urllib3, Pip Urllib3).
- The attack is network-based and needs no privileges: restrict exposure (ACLs, VPN, WAF) until patched.
- Apply the fixed version or the patch documented under Remediation.
- Exploitation requires user interaction: tighten email/web filtering and warn affected users.
- Search available logs for exploit probes matching the vulnerability class (cryptography), errors and authentication anomalies.
Affected scope
Vendor, product and versions as the sources word them.
Attack characteristics
The CVSS vector, decoded. It describes the attack, not your exposure to it.
Every base score collected
Sources score independently and may disagree; each row says who scored it and under which version.
| Score | Version | Severity | Expl. | Impact | Scored by |
|---|---|---|---|---|---|
| 7.6 | CVSS 4.0 | High | — | — | security-advisories@github.com via NIST National Vulnerability Database |
| 7.6 | CVSS 4.0 | High | — | — | GitHub_M via CVE Program (cve.org) e CISA ADP |
| 8.1 | CVSS 3.1 | High | 2.8 | 5.2 | nvd@nist.gov via NIST National Vulnerability Database |
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N (score shown at the top: nvd@nist.gov) Weakness MITRE
Weakness class according to MITRE’s CWE catalog.
EPSS over time FIRST
Oct 13, 2026 → Oct 15, 2026 · 3 reading(s) · max 0.24%
Detection
Read off the CVSS vector and the weakness class. Starting points, not tested rules.
- Prioritize edge telemetry for the network-reachable component (proxy, WAF, IDS/IPS).
- Check TLS negotiations and unexpected certificates in the component’s traffic.
Timeline
What happened to this CVE, newest first.
- 2026
- Fix documented
- Affected products added · pip/urllib3
- Affected products added · urllib3/urllib3
- SSVC assessment updated
- Record published
- Fix documented
- CVSS changed · 8.1
- Source status changed · → Analyzed
- Record created in this database
- CVE published
Source activity
Repeated readings are counted rather than listed.
- 1× References added · Oct 13, 2026 – Oct 13, 2026
- 1× Official description updated · Oct 13, 2026 – Oct 13, 2026
References
7 on the record
- github.com/urllib3/urllib3/security/advisories/GHSA-8988-9cw3-xx77
- github.com/urllib3/urllib3/commit/07408cec79d1856d81bb42c74a904a24fdb9e465
- github.com/urllib3/urllib3/commit/b6447295fff7b38fdffc67e0df9712d60cef3cc3
- github.com/urllib3/urllib3/pull/5093
- nvd.nist.gov/vuln/detail/CVE-2026-97687
- github.com/urllib3/urllib3/releases/tag/2.8.0
- github.com/advisories/GHSA-8988-9cw3-xx77
Elsewhere on this site
Related CVEs (same products)
- High CVE-2026-97689 urllib3: HTTPResponse.stream()/read_chunked() buffers an unbounded chunk-size line into memory 16d
- Medium CVE-2026-97688 urllib3: Chunked Deflate streaming can enter an infinite loop 16d
- Medium CVE-2026-44431 urllib3: Sensitive headers forwarded across origins in proxied low-level redirects May 13, 2026
- High CVE-2026-44432 urllib3: Decompression-bomb safeguards bypassed in parts of the streaming API May 13, 2026
- High CVE-2026-21441 urllib3 vulnerable to decompression-bomb safeguard bypass when following HTTP redirects (streaming API) Jan 7, 2026
- High CVE-2025-66471 urllib3 Streaming API improperly handles highly compressed data Dec 5, 2025
Not in any source we poll
Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.
- No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
- No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
- No exploit packet captures, log samples, or incident case IDs supplied.
Answered from this record
Text assembled only from the fields above — no additional claims.
What should defenders know first?
CVE-2026-97687 is "urllib3: HTTPS proxy TLS configuration may be ignored or overridden", rated High. It affects Urllib3 (Python); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. CVSS 8.1 describes technical severity. EPSS 0.21% estimates the probability of exploitation in 30 days; neither replaces your asset context. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.
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