Affected: OpenSSL, Siemens RUGGEDCOM RM1224 LTE(4G) EU, Siemens RUGGEDCOM RM1224 LTE(4G) NAM, Siemens RUGGEDCOM RST2428P, Siemens SCALANCE M804PB, Siemens SCALANCE M812-1 ADSL-Router, Siemens SCALANCE M816-1 ADSL-Router, Siemens SCALANCE M826-2 SHDSL-Router, Siemens SCALANCE M874-2, Siemens SCALANCE M874-3 and 22 more

Issue summary: Some non-default TLS server configurations can cause unbounded memory growth when processing TLSv1.3 sessions

Impact summary: An attacker may exploit certain server configurations to trigger unbounded memory growth that would lead to a Denial of Service

This problem can occur in TLSv1.3 if the non-default SSL_OP_NO_TICKET option is being used (but not if early_data support is also configured and the default anti-replay protection is in use). In this case, under certain conditions, the session cache can get into an incorrect state and it will fail to flush properly as it fills. The session cache will continue to grow in an unbounded manner. A malicious client could deliberately create the scenario for this failure to force a Denial of Service. It may also happen by accident in normal operation.

This issue only affects TLS servers supporting TLSv1.3. It does not affect TLS clients.

The FIPS modules in 3.2, 3.1 and 3.0 are not affected by this issue. OpenSSL 1.0.2 is also not affected by this issue.