HighCVE-2026-97687

    urllib3: HTTPS proxy TLS configuration may be ignored or overridden (CVE-2026-97687)

    Published Last modified Sources: Red Hat, SUSE, Ubuntu, BSI, Msrc Update Guide, CVE.org, OSV, Hersteller

    What is affected, what to do

    A flaw was found in urllib3. This vulnerability allows a remote attacker on the network to intercept and alter data transmitted through an HTTPS proxy.

    Update urllib3 to version 2.8.0.

    Affected
    • Urllib3 gte 1.26.0, < 2.8.0..*

    Not sure whether and how you are affected? Ask a question about this vulnerability

    Metrics

    8.1

    Priority

    XIEM Effective CVSS: highest available CVSS rating from NVD and vendor data.

    Source: NVD, CVSS v3

    8.1

    CVSS v3

    Severity High on the scale from 0 to 10.

    Source: Red Hat, SUSE, Ubuntu, BSI, Msrc Update Guide, CVE.org, OSV, Hersteller

    0.2 %

    EPSS score

    Low — model estimates < 1% exploitation likelihood.

    Source: FIRST EPSS, percentile 10.0

    Show all metrics
    Severity
    High
    Priority score

    The priority score is a consolidated metric that condenses several individual signals into a single, action-guiding ranking: technical severity (CVSS), exploitation likelihood (EPSS), known-exploited status (KEV) and the context of the affected asset. The aim is to answer the only truly important question in vulnerability management: what first?

    Read in glossary
    71.29
    Exploit maturity

    An exploit is code or a technique that specifically uses a concrete vulnerability to force unintended behaviour — such as executing code or escalating privileges. It is the tool that turns a theoretical flaw into a practical attack.

    Read in glossary
    no public PoC known
    XIEM Effective CVSS

    XIEM® is the tiered managed-security operating model from NEOSEC and a registered trademark of NEOSEC GmbH. It extends classic SIEM — the central collection, normalisation and correlation of security-relevant events — with endpoint forensics, network visibility and deception technology, and consolidates them into three building tiers: Sentry, Orchestrate and Command.

    Read in glossary
    8.1
    CVSS v3

    CVSS is the globally established, open standard for assessing the technical severity of a vulnerability on a scale from 0 to 10. It describes how easily a flaw can be exploited and what damage it can cause — but not how likely its actual exploitation is. CVSS and the complementary EPSS deliberately answer different questions.

    Read in glossary
    8.1
    CVSS v4

    CVSS is the globally established, open standard for assessing the technical severity of a vulnerability on a scale from 0 to 10. It describes how easily a flaw can be exploited and what damage it can cause — but not how likely its actual exploitation is. CVSS and the complementary EPSS deliberately answer different questions.

    Read in glossary
    7.6
    EPSS score

    The EPSS score is the absolute model output for an individual vulnerability: the estimated probability of real-world exploitation within the next 30 days, expressed as a value between 0 and 1 (i.e. 0 % to 100 %). A score of 0.42 means „the model estimates a 42 % chance of real-world exploitation within 30 days“.

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    0.2 %
    Low — model estimates < 1% exploitation likelihood.
    EPSS percentile

    The EPSS percentile is the relative position of a vulnerability within all EPSS-scored CVEs, expressed as a value between 0 and 1. A percentile of 0.90 means „this CVE has a higher EPSS score than 90 % of all other scored CVEs“. Unlike the EPSS score, it is not a probability — but a positioning within a ranking.

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    10.0
    Elevated — this CVE ranks above at least 10% of all CVEs scored today.
    KEV status

    The KEV catalogue is a list maintained by the US authority CISA of vulnerabilities for which active exploitation in the wild has been confirmed. It answers not the question „how severe?“ but „is it already being attacked?“ — thereby sharply prioritising patching.

    Read in glossary
    —
    Published
    CWE

    CWE is a catalogue of typical weakness types in software and hardware — such as flawed input validation, unsafe memory handling or poor authentication. Where a CVE names a concrete vulnerability in a concrete product, a CWE describes the underlying class of defect.

    Read in glossary
    CWE-295, CWE-440

    Classification under NIS2 and CRA

    Rule-based classification from exploitation status and severity. It does not replace a case-by-case assessment.

    NIS2

    NIS2 is EU Directive (EU) 2022/2555 to raise the level of cybersecurity across the Union. It substantially broadens obligations compared with the first NIS directive: more sectors, mandatory risk management, staged reporting duties and personal accountability of senior management.

    Read in glossary
    High technical severity: assess and remediate the vulnerability in vulnerability handling under Art. 21(2)(e) NIS2 and document the decision.
    CRA

    The CRA is EU Regulation (EU) 2024/2847 setting horizontal cybersecurity requirements for „products with digital elements“ — from industrial controllers and software to connected consumer devices. For the first time manufacturers must ensure security across the entire product lifecycle, handle vulnerabilities and provide security updates.

    Read in glossary
    From 11.12.2027, Annex I Part II CRA requires manufacturers of affected products with digital elements to handle vulnerabilities without delay and provide security updates.
    ISO/IEC 27001

    ISO/IEC 27001 is the internationally leading standard for an information security management system (ISMS). It describes a risk-based, process-oriented framework to systematically plan, implement, review and improve information security.

    Read in glossary
    Control A.8.8, management of technical vulnerabilities: assess relevance to your systems, plan remediation and keep evidence.

    Description

    A flaw was found in urllib3. This vulnerability allows a remote attacker on the network to intercept and alter data transmitted through an HTTPS proxy. The issue occurs when target-server Transport Layer Security (TLS) settings inadvertently overwrite the proxy's TLS configuration, which can disable certificate verification on reused connection contexts. Consequently, an attacker can impersonate the proxy to monitor or modify forwarded traffic or capture client credentials.

    Source: redhat_csaf, suse_csaf, Ubuntu Security Notices, BSI CSAF, BSI WID Portal, Microsoft Security Update Guide, NVD (NIST), OSV (Open Source Vulnerabilities), cvelistv5, GitHub Security Advisories

    Affected products

    The following versions are affected. Older releases of the same product line are also vulnerable unless stated otherwise.

    Affected products
    VendorProductAffected versionsFixed in
    urllib3urllib3
    • ≥ 1.26.0, < 2.8.0
    • —
    pythonurllib3
    • 1.26.0 – < 2.8.0
    • 2.8.0
    Red HatEnterprise Linux
    • 10
    • 9
    • —
    • —

    Affected operating systems

    Affected operating systems
    FamilyVendorProductVersion
    Linuxubuntupython-urllib3bionic
    Linuxubuntupython-urllib3focal
    Linuxubuntupython-urllib3jammy
    Linuxubuntupython-urllib3noble
    Linuxubuntupython-urllib3resolute

    Weakness classes (CWE)

    • CWE-295Improper Certificate Validation

      Base

      The product does not validate, or incorrectly validates, a certificate.

      Entry at MITRE CWE-295

    • CWE-440Expected Behavior Violation

      Base

      A feature, API, or function does not perform according to its specification.

      Entry at MITRE CWE-440

    References & sources

    • github.comurllib3/urllib3/security/advisories/GHSA-8988-9cw3-xx77x_refsource_CONFIRM
    • github.comurllib3/urllib3/pull/5093x_refsource_MISC
    • github.comurllib3/urllib3/commit/07408cec79d1856d81bb42c74a904a24fdb9e465x_refsource_MISC
    • github.comurllib3/urllib3/commit/b6447295fff7b38fdffc67e0df9712d60cef3cc3x_refsource_MISC
    • github.comurllib3/urllib3/releases/tag/2.8.0x_refsource_MISC
    • NVD (NIST)vuln/detail/CVE-2026-97687advisory
    • github.comurllib3/urllib3package
    • pypi.orgproject/urllib3package
    • GitHub Security Advisoriesadvisories/GHSA-8988-9cw3-xx77advisory

    Reanalysis & status changes

    Chronological NVD audit events for this CVE — reanalyses, CVSS updates, CPE diffs.

    1. Initial Analysisnvd@nist.gov

      • CVSS V3.1: after AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N
      • CPE Configuration: after OR *cpe:2.3:a:python:urllib3:*:*:*:*:*:*:*:* versions from (including) 1.26.0 up to (excluding) 2.8.0
      • Reference Type: after GitHub, Inc.: https://github.com/urllib3/urllib3/commit/07408cec79d1856d81bb42c74a904a24fdb9e465 Types: Patch
      • Reference Type: after GitHub, Inc.: https://github.com/urllib3/urllib3/commit/b6447295fff7b38fdffc67e0df9712d60cef3cc3 Types: Patch

    2. CVE Modified134c704f-9b21-4f2e-91b3-4a467353bcc0

      • SSVC: after {"id":"CVE-2026-97687","role":"CISA Coordinator","options":[{"exploitation":"none"},{"automatable":"no"},{"technicalI…

    3. New CVE Receivedsecurity-advisories@github.com

      • Description: after 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.
      • CVSS V4.0: after AV:N/AC:L/AT:P/PR:N/UI:P/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
      • CWE: after CWE-295
      • CWE: after CWE-440