MEDIUM 5.3 Microsoft

CVE-2023-40217

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.)

Microsoft Security Update 2023-Aug: 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.)

Affected Products

References

Published: 2023-08-08 · Source: Microsoft · Feed updated: 2026-08-14
This medium severity vulnerability with a CVSS score of 5.3 was published on 2023-08-08 via Microsoft. Affected: cbl2 python3 3.9.19-1 on CBL Mariner 2.0.
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