What is the CVSS score of CVE-2021-21798?

CVE-2021-21798 has a CVSS 3.1 base score of 7.8 (High). CVSS vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H. EPSS exploitation probability: 16.1%.

Is there a public PoC exploit available for CVE-2021-21798?

Yes, a public proof-of-concept exploit is available for CVE-2021-21798. Prioritise patching immediately. EPSS: 16.1%.

Nitro Pro CVE-2021-21798

HIGH

Return of Stack Variable Address (CWE-562)

2021-09-15 talos-cna@cisco.com

RCE Nitro Pro Gonitro

7.8

CVSS 3.1 · NVD

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Vulnerability Assessment

Weakness	CWE CWE-562
Impact	CVSS score of 7.8 (HIGH). Attack characteristics: local attack vector, low complexity, no privileges required, user interaction required. Public proof-of-concept exploit code is available.
Exploit ScenarioDerived	Successful exploitation could compromise the high-severity affected system.

This Week Schedule remediation this week. Why: HIGH severity + EPSS > 10%.

No patch listed yet 16.1% exploitation probability (EPSS)

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AnalysisAI

An exploitable return of stack variable address vulnerability exists in the JavaScript implementation of Nitro Pro PDF. Rated high severity (CVSS 7.8), this vulnerability is no authentication required, low attack complexity. Public exploit code available and no vendor patch available.

RemediationAI

No vendor patch is available at time of analysis. Monitor vendor advisories for updates. Apply vendor patches when available. Implement network segmentation and monitoring as interim mitigations.

Affects your stack

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Technical ContextAI · show details

This vulnerability is classified under CWE-562. An exploitable return of stack variable address vulnerability exists in the JavaScript implementation of Nitro Pro PDF. A specially crafted document can cause a stack variable to go out of scope, resulting in the application dereferencing a stale pointer. This can lead to code execution under the context of the application. An attacker can convince a user to open a document to trigger the vulnerability. Affected products include: Gonitro Nitro Pro.

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Exploit and PoC references, threat intelligence from 22 sources

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Severity by source

NVD PRIMARY 7.8 HIGH

AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

Primary rating from NVD · only source for this CVE.

CVSS VectorNVD

Attack Vector

Local

Attack Complexity

Low

Privileges Required

None

User Interaction

Required

Scope

Unchanged

Confidentiality

High

Integrity

High

Availability

High

DescriptionNVD

An exploitable return of stack variable address vulnerability exists in the JavaScript implementation of Nitro Pro PDF. A specially crafted document can cause a stack variable to go out of scope, resulting in the application dereferencing a stale pointer. This can lead to code execution under the context of the application. An attacker can convince a user to open a document to trigger the vulnerability.

Threat Intelligence Overview

EPSS Score

16.1%

Top 3% exploitable

Exploit

POC

Public exploit code exists

Data Quality

2 sources

Confidence: Low

NVD

CVE.org

EPSS

How this decision was reached

The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.

SignalValue

Severity HIGH

CISA KEV No

Public POC Yes

EPSS 16.1%

Patch available No

Active threat Yes

Deciding rule

HIGH severity + EPSS > 10%

What every action level means

Emergency Immediate action required. Criteria: CRITICAL + in CISA KEV (actively exploited) without patch, OR CRITICAL + EPSS > 30% without patch, OR CRITICAL + active threat signals without patch.

Act Now Prioritize within 24-48h. Criteria: in KEV with patch available, OR CRITICAL + public POC, OR HIGH + EPSS > 10%, OR CRITICAL + active threat, OR any CRITICAL severity.

This Week Schedule remediation this week. Criteria: HIGH severity (CVSS 7.0-8.9). Patch within normal change window.

This Month Plan within 30 days. Criteria: MEDIUM severity (CVSS 4.0-6.9), lower exploitation probability. Include in regular patch cycle.

Monitor Track and reassess. Criteria: LOW severity (CVSS 0.1-3.9), minimal exploitation risk. No immediate action needed.

SSVC AssessmentENISA

SSVC Decision· derived

Scheduled

Exploitation· derived

Poc

System Exposure· derived

Small

Automatable· derived

Human Impact· derived

Medium

Priority Score

Low Medium High Critical

KEV: 0

EPSS: +16

CVSS: +39

PoC: +20

Weaponized: 0

Threat intel: 0

Gov advisory: 0

Attack Technique

Remote Code Execution CRITICAL

Remote Code Execution represents the critical moment when an attacker successfully runs arbitrary code on a target system without physical access.

Affected Products (CPE)NVD

cpe:2.3:a:gonitro:nitro_pro:13.31.0.605:*:*:*:*:*:*:*

cpe:2.3:a:gonitro:nitro_pro:13.33.2.645:*:*:*:*:*:*:*

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