CVE-2021-31158

In the Query Engine in Couchbase Server 6.5.x and 6.6.x through 6.6.1, Common Table Expression queries were not correctly checking the user's permissions, allowing read-access to resources beyond what those users were explicitly allowed to access.

Published: 2021-05-19 Last update: 2026-06-16 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2021-31158 is rated Moderate Risk (43.4/100): CVSS Medium severity, with low exploitation likelihood (EPSS 0.70%). Review affected assets and schedule remediation.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2021-31158

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-06-15 0.17% 0.70% +0.54%
2 2025-03-30 0.35% 0.17% -0.18%
3 2025-03-29 — 0.35% —

Full EPSS history (9 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2021-31158

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
6.5 3.1 MEDIUM
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:L)
A normal user session is enough; they don’t have to be admin.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:H)
Serious risk that confidential data gets exposed in a big way.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:N)
Service keeps running; no real outage angle.
 2.8 3.6 [email protected]
4.0 2.0 MEDIUM
AV:N/AC:L/Au:S/C:P/I:N/A:N Click to expand
Access vector (AV:N)
Can be exploited remotely over network reachability.
Access complexity (AC:L)
Exploitation conditions are straightforward and predictable.
Authentication (AU:S)
A single authentication is required.
Confidentiality impact (C:P)
Partial confidentiality impact.
Integrity impact (I:N)
No integrity impact.
Availability impact (A:N)
No availability impact.
 8.0 2.9 [email protected]

Weakness enumeration for CVE-2021-31158

Affected software / configurations for CVE-2021-31158

Vendor Product Version Raw CPE
couchbase couchbase_server >= 6.5.0, < 6.6.2 cpe:2.3:a:couchbase:couchbase_server:*:*:*:*:*:*:*:*

References for CVE-2021-31158

cvelogic Threat Intelligence