CVE-2023-40217

MEDIUMNVD 5.35.3—
EchelonGraph scoreMEDIUM confidence

Score 5.3 from GitHub Security Advisory published 2023-08-25. NVD baseline CVSS 5.3; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: ghsa, nvd
5.3
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS: 1%CVSS: 5.3Exploit: NoneExposed: 0

A fix is available — apply it.

An issue was discovered in Python before 3.8.18, 3.9.x before 3.9.18, 3.10.x before 3.10.13, and 3.11.x before 3.11.5. It primarily affects servers (such as HTTP servers) that use TLS client authentication. If a TLS server-side socket is created, receives data into the socket buffer, and then is closed quickly, there is a brief window where the SSLSocket instance will detect the socket as "not connected" and won't initiate a handshake, but buffered data will still be readable from the socket buffer. This data will not be authenticated if the server-side TLS peer is expecting client certificate authentication, and is indistinguishable from valid TLS stream data. Data is limited in size to the amount that will fit in the buffer. (The TLS connection cannot directly be used for data exfiltration because the vulnerable code path requires that the connection be closed on initialization of the SSLSocket.)

CVSS v3
5.3
EG Score
5.3(medium)
EPSS
52.4%
KEV
Not listed

Published

August 25, 2023

Last Modified

November 3, 2025

References (12)

Vendor Advisories for CVE-2023-40217(1)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Patch Availability(25)

Vendor / EcosystemFixed in / PatchReleasedSource
ubuntupython3.5-venv (3.5.2-2ubuntu0~16.04.13+esm12) @ xenial2026-05-23ubuntu
ubuntupython2.7-minimal (2.7.18-13ubuntu1.5) @ jammy2026-05-23ubuntu
ubuntupython3.8-venv (3.8.0-3ubuntu1~18.04.2+esm2) @ bionic2026-05-23ubuntu
ubuntupython3.11-venv (3.11.4-1~23.04.1) @ lunar2026-05-23ubuntu
redhatpython-0:2.7.5-94.el7_92023-11-13redhat
redhatpython3-0:3.6.8-21.el7_92023-11-08redhat
redhatrh-python38-python-0:3.8.18-2.el72023-11-08redhat
redhatpython-0:2.6.6-70.el6_102023-11-02redhat
redhatpython39:3.9-8040020230922214438.63cd9eba2023-10-24redhat
redhatpython39-devel:3.9-8060020230922214243.6a6313992023-10-24redhat
redhatpython27:2.7-8040020231004234308.7c6da4642023-10-23redhat
redhatpython3-0:3.6.8-51.el8_8.22023-10-23redhat
redhatpython3-0:3.6.8-15.1.el8_1.22023-10-23redhat
redhatpython27:2.7-8080020231004233750.392b0bf12023-10-23redhat
redhatpython39-devel:3.9-8080020230922214114.93c2fc2f2023-10-23redhat
redhatpython27:2.7-8010020231004234533.208b345f2023-10-23redhat
redhatpython27:2.7-8020020231004234409.c9f5743f2023-10-23redhat
redhatpython3-0:3.6.8-39.el8_4.32023-10-23redhat
redhatpython27:2.7-8060020231004234102.2aa69ce42023-10-23redhat
redhatpython3-0:3.6.8-47.el8_6.22023-10-09redhat
redhatpython3-0:3.6.8-24.el8_2.22023-10-09redhat
redhatpython3.9-0:3.9.16-1.el9_2.22023-10-05redhat
redhatpython3.9-0:3.9.10-4.el9_0.22023-10-05redhat
redhatpython3.11-0:3.11.2-2.el9_2.22023-10-05redhat
redhatpython3.11-0:3.11.2-2.el8_8.22023-10-05redhat

Patches are aggregated from vendor advisories (Red Hat, Microsoft, Cisco, GitHub) and package ecosystems (OSV, GHSA). Multiple rows for the same upstream release have been deduplicated.

Additional Vendor Advisories

(24)

Vendors that published advisories for this CVE beyond the curated set above. Broader coverage but minimal per-row detail — click through for the original advisory.

Data Freshness Timeline

(refreshed 10× in last 7d / 46× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

Showing the most recent 100 of 107 total refreshes for this CVE.

  1. 2026-07-22 14:06 UTCEPSS rescore
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Frequently asked(5)

What is CVE-2023-40217?
CVE-2023-40217 is a medium vulnerability published on August 25, 2023. An issue was discovered in Python before 3.8.18, 3.9.x before 3.9.18, 3.10.x before 3.10.13, and 3.11.x before 3.11.5. It primarily affects servers (such as HTTP servers) that use TLS client authentication. If a TLS server-side socket is created, receives data into the socket buffer, and then is…
When was CVE-2023-40217 disclosed?
CVE-2023-40217 was first published in the National Vulnerability Database on August 25, 2023, with the most recent update on November 3, 2025. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2023-40217 actively exploited?
CVE-2023-40217 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 52.4% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2023-40217?
CVE-2023-40217 has a CVSS v3 base score of 5.3 (NVD).
How do I remediate CVE-2023-40217?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2023-40217, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

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