What is CVE-2021-20376?

CVE-2021-20376 is a medium-severity vulnerability in IBM Sterling B2b Integrator, classified under Observable Discrepancy. CVSS score: 4.3/10. Published 2021-10-07.

How severe is CVE-2021-20376?

Medium severity. CVSS v3 base score is 4.3 out of 10.

Vulnerability in IBM Sterling B2b Integrator

CVE-2021-20376

IBM Sterling File Gateway 2.2.0.0 through 6.1.1.0 could allow an authenticated attacker to enumerate usernames due to there being an observable discrepancy in returned messages. IBM X-Force ID: 195568.

Published 2021-10-07 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 4.3 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N.

EPSS exploit prediction

EPSS: 0.007 (52.4th percentile), scored 2026-10-01.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 52nd percentile — 52.4% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.007 · newest: 0.007 · change: 0.000

Affected products

IBM Sterling B2b Integrator
IBM Sterling File Gateway — versions 2.2.0.0, 6.0.0.0, 5.2.6.5_3

Weakness classification (CWE)

CWE-203 — Observable Discrepancy

References

www.ibm.com/support/pages/node/6496789 (Patch, Vendor Advisory)
exchange.xforce.ibmcloud.com/vulnerabilities/195568 (VDB Entry, vdb-entry, Vendor Advisory)

Frequently asked questions

What is CVE-2021-20376?: CVE-2021-20376 is a medium-severity vulnerability in IBM Sterling B2b Integrator, classified under Observable Discrepancy. CVSS score: 4.3/10. Published 2021-10-07.
How severe is CVE-2021-20376?: Medium severity. CVSS v3 base score is 4.3 out of 10.