Comment 0 for bug 2043114

We have a physical server running Ubuntu 20.04.6 LTS (amd64) and openssh-server 1:8.2p1-4ubuntu0.9. Sometimes sshd crashes with a segmentation fault on remote login with key authentication:
[193107.651745] sshd[1229630]: segfault at 5557eba6a008 ip 00007f2326a2ca53 sp 00007ffcba40c510 error 4 in libc-2.31.so[7f23269b8000+178000]

We’ve changed only the following values in the stock sshd_config file:

LogLevel DEBUG
PasswordAuthentication no
MaxStartups 100:30:100

The server is used for automated software testing, and sometimes our test suite might make a large amount of SSH connections in a short period of time, which seems to be correlated with the crashes. But at the same time, I have to note that the connection count was not near the MaxStartups limit, and we’ve had crashes before adding that setting.
Since the backtrace shows the debug logging function in the stack, we’re currently experimenting with using `LogLevel INFO` to try and isolate the issue.

I am attaching the backtrace. I could provide the full dump file, although I am hesitant due to the possibility of private keys or other sensitive information leaking.

# apt-cache policy openssh-server
openssh-server:
  Installed: 1:8.2p1-4ubuntu0.9
  Candidate: 1:8.2p1-4ubuntu0.9
  Version table:
 *** 1:8.2p1-4ubuntu0.9 500
        500 http://mirrors.storpool.com/ubuntu/archive focal-updates/main amd64 Packages
        500 http://security.ubuntu.com/ubuntu focal-security/main amd64 Packages
        100 /var/lib/dpkg/status
     1:8.2p1-4 500
        500 http://mirrors.storpool.com/ubuntu/archive focal/main amd64 Packages