Loading vulnerability…
CVE-2021-21994 is an authentication bypass vulnerability in the Small Footprint CIM Broker (SFCB) component as used in VMware ESXi. The vulnerability allows a remote attacker with network access to port 5989 to bypass SFCB authentication by sending a specially crafted request, potentially gaining unauthorized access to management functions exposed by SFCB.
Mallory correlates every CVE against your assets, your vendors, and active adversary campaigns. Know which vulnerabilities matter for you, not just which ones are loud.
What it means. What to do now. Patch path, mitigations, and the assume-compromise checklist.
What an attacker gets, and what they’ve been doing with it.
If you can’t patch tonight, do this now.
Patch, then assume compromise.
1 valid exploit after Mallory filtered fakes, detection scripts, and README-only repos.
Repository contains two Python tools and a README documenting a working PoC for CVE-2021-21994 against VMware ESXi SFCB. `sfcb_probe.py` is a research harness with `check` and `fuzz` modes: it builds raw HTTPS CIM-XML POST requests to `/cimom`, validates an authentication oracle, and mutates Authorization/header formatting to discover bypass conditions. It includes low-level TLS socket handling, raw HTTP request construction, response status parsing, and verdict classification based on HTTP status and CIM body presence. `sfcb_exploit.py` is the operational exploit PoC built on top of the probe helpers. It hardcodes the bypass header `Authorization: Basic cm9vdA==` and provides modes to verify the bypass, enumerate class names, enumerate instance names or full instances, inspect methods, invoke methods, and send arbitrary CIM-XML from a file. The exploit capability is unauthenticated access to the ESXi CIM broker for information disclosure, especially host inventory and account enumeration, rather than remote code execution. The README states the root cause: if the Basic auth token does not decode into a `user:password` pair containing `:`, sfcbd skips authentication and forwards the request into the CIMOM. The repository is therefore a real, operational network exploit/PoC for auth bypass and unauthenticated CIM data access on vulnerable ESXi builds.
Products and vendors Mallory has correlated with this vulnerability. Open in Mallory to drill down to specific CPE configurations and version ranges.
Vendor-confirmed product mapping. Mallory continuously reconciles this list against your asset inventory.
No public activity tracked yet. Mallory keeps watching.
No public activity observed for this vulnerability.
Query your assets running an affected version, and investigate the blast radius.
Every observed campaign linking this CVE to a named adversary.
Malware families riding this exploit, with evidence and IOCs.
YARA, Sigma, Snort, and vendor rules, auto-deployed to your SIEM.
Cross-references every affected SKU, including bundled OEM variants.
Community discussion across Reddit, Mastodon, and other social sources.