View at Official ubuntu advisory, NVD, CVE.org · CVE detail
Freshness: upstream tracker timestamp is available; use API updated time as primary recency signal.
CVE-2011-2523 high priority: Ubuntu including 1 source packages (vsftpd), 6 status rows across 6 suites (hardy, lucid, maverick, natty, oneiric, upstream): not-affected 5, needs-triage 1.
vsftpd 2.3.4 downloaded between 20110630 and 20110703 contains a backdoor which opens a shell on port 6200/tcp.