How severe is CVE-2021-43963?

CVE-2021-43963 has a CVSS 3.x base score of 8.1, rated high severity. It is exploitable over network with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability none.

Is CVE-2021-43963 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (39th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-43963?

CVE-2021-43963 affects Couchbase Sync Gateway. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2021-43963?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

When was CVE-2021-43963 published?

CVE-2021-43963 was published on 2021-12-07 and last updated on 2026-06-17.

CVE-2021-43963

CVE-2021-43963 is a high-severity vulnerability in Couchbase Sync Gateway with a CVSS 3.x base score of 8.1. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-200.

Key facts

Severity: High (CVSS 3.x base score 8.1)
CVSS v2: 5.5
EPSS exploit prediction: 1% (39th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-200
Affected product: Couchbase Sync Gateway
Published: 2021-12-07
Last modified: 2026-06-17

Description

An issue was discovered in Couchbase Sync Gateway 2.7.0 through 2.8.2. The bucket credentials used to read and write data in Couchbase Server were insecurely being stored in the metadata within sync documents written to the bucket. Users with read access could use these credentials to obtain write access. (This issue does not affect clusters where Sync Gateway is authenticated with X.509 client certificates. This issue also does not affect clusters where shared bucket access is not enabled on Sync Gateway.)

Frequently asked questions

What is CVE-2021-43963?: An issue was discovered in Couchbase Sync Gateway 2.7.0 through 2.8.2. The bucket credentials used to read and write data in Couchbase Server were insecurely being stored in the metadata within sync documents written to the bucket. Users with read access could use these credentials to obtain write access. (This issue does not affect clusters where Sync Gateway is authenticated with X.509 client certificates. This issue also does not affect clusters where shared bucket access is not enabled on Sync Gateway.)
How severe is CVE-2021-43963?: CVE-2021-43963 has a CVSS 3.x base score of 8.1, rated high severity. It is exploitable over network with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability none.
Is CVE-2021-43963 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (39th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-43963?: CVE-2021-43963 affects Couchbase Sync Gateway. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-43963?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
When was CVE-2021-43963 published?: CVE-2021-43963 was published on 2021-12-07 and last updated on 2026-06-17.

References

https://www.couchbase.com/alerts

Affected products (1)

cpe:2.3:a:couchbase:sync_gateway:*:*:*:*:*:*:*:*

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