Upon further investigation, the culprit turns out to be the sshd plugin
, which we upgraded to v3.1.0 at the same time as the core. Downgrading sshd to to 3.0.3 (the detached version in the 2.332.1 war) restores the correct behavior (no hangs). All sshd versions 3.0.4 through 3.228.v4c9f9e652c86 (latest available at this time) exhibit the hang problem. Interestingly, sshd 3.0.4 brought with it an upgrade to SSHD itself
(from 1.x to 2.x).
It's an unfortunate loss of functionality, since we cannot remain on sshd 3.0.3. Jenkins developers -- is a Jira ticket warranted for this?