CVE-2021-34473
This CVE is being exploited. Apply the vendor fix, or take the service off the internet until you can, then check your logs for attempts.
What it is
Microsoft Exchange Server Remote Code Execution Vulnerability
Live exploitation on the huntback network (30 days)
Detection
Evidence
Confirmed exploited. Our decoys have seen it exploited before (8 attempts), not in the last 14 days; CISA added it to KEV 1835 days ago.
Last attempt. 8 attempts on our decoys, 0 in the last 14 days
First exploitation attempt on our decoys
Added to CISA Known Exploited Vulnerabilities
Published
Exploit code published (Metasploit)
Nuclei detection template available
Observed: our own decoys saw it. Reported: CISA, the vendor or another named source says so. Weaponised: public exploit code or a scanner template exists. Methodology
Questions
Is CVE-2021-34473 being exploited in the wild?
Yes. The huntback decoy network captured 8 exploitation attempts from 3 distinct source IPs; the most recent was on 2026-10-17. It is also in the CISA KEV catalogue.
Can CVE-2021-34473 be detected on the network?
Yes. huntback carries a network signature for CVE-2021-34473, so attempts against a decoy are tagged in real time.
How huntback helps
Deploy a decoy that emulates Exchange Server and you will see every attempt at this CVE the moment it lands, with the full payload, the attacker's infrastructure, and any stage-2 loader. Then huntback can scan the attacker back.
Related
NVD record → Browse all CVEs → Live malware and C2 finds → Novel-attack discovery → Deploy a decoy →API
This record, with its evidence timeline, as JSON:
curl -H "X-API-Key: $HUNTBACK_KEY" https://app.huntback.io/api/v1/evidence/CVE-2021-34473