CVE-2021-31330

Exp

A Cross-Site Scripting (XSS) vulnerability exists within Review Board versions 3.0.20 and 4.0 RC1 and earlier. An authenticated attacker may inject malicious Javascript code when using Markdown editing within the application which remains persistent.

Published: 2022-05-11 Last update: 2026-06-16 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2021-31330 is rated Exploit Available (54.6/100): CVSS Medium severity, with medium exploitation likelihood (EPSS 0.77%). 1 public exploit reference(s) are indexed (Exploit-DB). Public exploits are available—assess exposure, apply mitigations, and prioritize patching.

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

Public exploit references (Exploit-DB) for CVE-2021-31330

EDB-ID Source Kind Published Link
— nvd_ref exploit_tag Exploit-DB ↗

Exploit prediction scoring system (EPSS) score for CVE-2021-31330

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 0.48% 0.77% +0.28%
2 2026-05-22 0.59% 0.48% -0.11%
3 2025-11-21 — 0.59% —

Full EPSS history (13 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2021-31330

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
5.4 3.1 MEDIUM
CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/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:R)
A real person has to do something—click, install, enable—otherwise it doesn’t land.
Scope (S:C)
Breaking this can reach past the original component and bite other resources—bigger blast radius.
Confidentiality (C:L)
Some sensitive info could get out, but not a total data dump.
Integrity (I:L)
Attackers could change some data, but it’s limited—not everything goes.
Availability (A:N)
Service keeps running; no real outage angle.
 2.3 2.7 [email protected]
3.5 2.0 LOW
AV:N/AC:M/Au:S/C:N/I:P/A:N Click to expand
Access vector (AV:N)
Can be exploited remotely over network reachability.
Access complexity (AC:M)
Exploitation needs some favorable conditions, but not exceptional ones.
Authentication (AU:S)
A single authentication is required.
Confidentiality impact (C:N)
No confidentiality impact.
Integrity impact (I:P)
Partial integrity impact.
Availability impact (A:N)
No availability impact.
 6.8 2.9 [email protected]

Weakness enumeration for CVE-2021-31330

Affected software / configurations for CVE-2021-31330

Vendor Product Version Raw CPE
reviewboard review_board 3.0.20 cpe:2.3:a:reviewboard:review_board:3.0.20:*:*:*:*:*:*:*
reviewboard review_board 4.0 cpe:2.3:a:reviewboard:review_board:4.0:beta1:*:*:*:*:*:*
reviewboard review_board 4.0 cpe:2.3:a:reviewboard:review_board:4.0:beta2:*:*:*:*:*:*
reviewboard review_board 4.0 cpe:2.3:a:reviewboard:review_board:4.0:rc1:*:*:*:*:*:*

References for CVE-2021-31330

cvelogic Threat Intelligence