Security Resilience

CVE-2023-40217

Python ≤ 3.8.18

Published
25 August 2023
Modified
03 November 2025
Patch / advisory
CVSS Score v3.1 5.3
Click a component to see what it means
Raw vectorCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
EPSS Score 0.0080 56th percentile
Risk Priority 46 floored blend · peak EPSS

CVSS and EPSS are reproduced from their sources (NVD, FIRST EPSS). Risk Priority is our own derived reading, not an NVD score.

Summary

CVE-2023-40217 is a medium-severity an unspecified weakness vulnerability in Python Python. Its CVSS base score is 5.3 (Medium).

Operationally, ranked in the top 44% of CVEs by exploit likelihood; it is not currently listed in the CISA KEV catalog.

EU & UK References

Vulnerability Data

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…

more

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.)

CWE(s)

Related Threats

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Affected Assets

python
python
≤ 3.8.18 · 3.9.0 — 3.9.18 · 3.10.0 — 3.10.13

Mitigating Controls

No mitigating controls mapped yet. The per-CVE control annotator has not reached this CVE.

References