NVD / CVE Program· CNA juniper

CVE-2021-0202: Junos OS: MX Series, EX9200 Series: Trio-based MPC memory leak when Integrated Routing and Bridging (IRB) interface is mapped to a VPLS instance or a Bridge-Dom

Noroxi assessment

Priority: Monitor (action score 30/100)

The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
Probability of exploitation in the next 30 days: 1% (FIRST EPSS); higher than 64.1% of all records.
Anyone who can reach it over the internet can trigger it. No account or password is required. No user action is required. No special conditions are required; it is repeatable.
Fixed version: Juniper Networks Junos OS 18.2R3-S6, 18.3R3-S4, 18.4R3-S6.

Low priority for now. Upgrade to Juniper Networks Junos OS 18.2R3-S6, 18.3R3-S4, 18.4R3-S6 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

On Juniper Networks MX Series and EX9200 Series platforms with Trio-based MPC (Modular Port Concentrator) where Integrated Routing and Bridging (IRB) interface is configured and it is mapped to a VPLS instance or a Bridge-Domain, certain network events at Customer Edge (CE) device may cause memory leak in the MPC which can cause an out of memory and MPC restarts. When this issue occurs, there will be temporary traffic interruption until the MPC is restored. An administrator can use the following CLI command to monitor the status of memory usage level of the MPC: user@device> show system resource-monitor fpc FPC Resource Usage Summary Free Heap Mem Watermark : 20 % Free NH Mem Watermark : 20 % Free Filter Mem Watermark : 20 % * - Watermark reached Slot # % Heap Free RTT Average RTT 1 87 PFE # % ENCAP mem Free % NH mem Free % FW mem Free 0 NA 88 99 1 NA 89 99 When the issue is occurring, the value of “% NH mem Free” will go down until the MPC restarts. This issue affects MX Series and EX9200 Series with Trio-based PFEs (Packet Forwarding Engines). Please refer to https://kb.juniper.net/KB25385 for the list of Trio-based PFEs. This issue affects Juniper Networks Junos OS on MX Series, EX9200 Series: 17.3R3-S8; 17.4R3-S2; 18.2R3-S4, 18.2R3-S5; 18.3R3-S2, 18.3R3-S3; 18.4 versions starting from 18.4R3-S1 and later versions prior to 18.4R3-S6; 19.2 versions starting from 19.2R2 and later versions prior to 19.2R3-S1; 19.4 versions starting from 19.4R2 and later versions prior to 19.4R2-S3, 19.4R3; 20.2 versions starting from 20.2R1 and later versions prior to 20.2R1-S3, 20.2R2. This issue does not affect Juniper Networks Junos OS: 18.1, 19.1, 19.3, 20.1.

HighCVSS 7.5 · v3.1—No exploit Fix available

BDU:2021-00994

Published: Jan 15, 2021
Updated: Jun 16, 2026
EPSS: 1.0% · 64th percentile
CWE: CWE-400

Report tools

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Action score

Monitor

Low priority for now.

CVSS: 30 / 40 · 7.5 / 10
CISA KEV: 0 / 30 · Not listed
EPSS: 0 / 30 · 1.0%

CNA vs NVD score

NVD: —
CNA · juniper: 7.5; NVD has not scored this yet; the score shown is the CNA’s.

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

Get told when this record changes

Not in KEV: no record of exploitation in the wild
No public exploit code on record
A fix has been released

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

Vendor	Product	CPE
juniper	junos	cpe:2.3:o:juniper:junos
juniper	ex9200	cpe:2.3:h:juniper:ex9200
juniper	mx10	cpe:2.3:h:juniper:mx10
juniper	mx10000	cpe:2.3:h:juniper:mx10000
juniper	mx10003	cpe:2.3:h:juniper:mx10003
juniper	mx104	cpe:2.3:h:juniper:mx104
juniper	mx150	cpe:2.3:h:juniper:mx150
juniper	mx2008	cpe:2.3:h:juniper:mx2008
juniper	mx2010	cpe:2.3:h:juniper:mx2010
juniper	mx2020	cpe:2.3:h:juniper:mx2020
juniper	mx204	cpe:2.3:h:juniper:mx204
juniper	mx240	cpe:2.3:h:juniper:mx240

and 5 more

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

juniper junos17.3
juniper junos17.4
juniper junos18.2
juniper junos18.3
juniper junos18.4
juniper junos19.2
juniper junos19.4
juniper junos20.2

Versions reported by the vendor

Affected version ranges reported by the assigning authority (juniper). Independent of NVD's CPE analysis and usually ahead of it.

Juniper Networks Junos OS
- 18.1, 19.1, 19.3, 20.1not affected
- 17.3R3-S8, 17.4R3-S2affected
- 18.2R3-S4 and later · before 18.2*affectedfixed in 18.2R3-S6
- 18.3R3-S2 and later · before 18.3*affectedfixed in 18.3R3-S4
- 18.4R3-S1 and later · before 18.4*affectedfixed in 18.4R3-S6
- 19.2R2 and later · before 19.2*affectedfixed in 19.2R3-S1
- 19.4R2 and later · before 19.4*affectedfixed in 19.4R2-S3, 19.4R3
- 20.2R1 and later · before 20.2*affectedfixed in 20.2R1-S3, 20.2R2

Same product

juniper: all records

Other highest-scoring records for the same primary product.

CVE-2023-36845Junos OS: EX and SRX Series: A PHP vulnerability in J-Web allows an unauthenticated to control an important environment variableKEV
98Now
CVE-2023-36846Junos OS: SRX Series: A vulnerability in J-Web allows an unauthenticated attacker to upload arbitrary filesKEV
79This week
CVE-2023-36844Junos OS: EX Series: A PHP vulnerability in J-Web allows an unauthenticated attacker to control important environment variablesKEV
78This week

Published before and after this one in the same product

← EarlierCVE-2020-1688Oct 16, 2020 · Junos OS: SRX and NFX Series: Insufficient Web API private key protection
26Monitor
← EarlierCVE-2020-1689Oct 16, 2020 · Junos OS: EX4300-MP/EX4600/QFX5K Series: High CPU load due to receipt of specific layer 2 frames when deployed in a Virtual Chassis configuration
26Monitor
Later →CVE-2021-0203Jan 15, 2021 · Junos OS: EX and QFX5K Series: Storm Control does not work as expected when Redundant Trunk Group is configured
34Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / package	Fixed version	Source
Juniper Networks Junos OS	18.2R3-S6	Vendor (CNA)
Juniper Networks Junos OS	18.3R3-S4	Vendor (CNA)
Juniper Networks Junos OS	18.4R3-S6	Vendor (CNA)
Juniper Networks Junos OS	19.2R3-S1	Vendor (CNA)
Juniper Networks Junos OS	19.4R2-S3, 19.4R3	Vendor (CNA)
Juniper Networks Junos OS	20.2R1-S3, 20.2R2	Vendor (CNA)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

No history yet (it accumulates with the daily EPSS job).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

No nightly-computed relations.

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

Attack conditions

Anyone who can reach it over the internet can trigger it.
No account or password is required.
No user action is required.
No special conditions are required; it is repeatable.

If successful

Confidentiality: none
Integrity: none
Availability: high · the service can be disrupted

Attack vector: Network
Attack complexity: Low
Privileges required: None
User interaction: None
Scope: Unchanged
Confidentiality impact: None
Integrity impact: None
Availability impact: High

Weakness class (CWE)

CWE-400 · Uncontrolled Resource Consumption

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

nvd-secondary

Root cause

Code that parses nested structures sets no depth or size limit. A small input can turn into a disproportionate processing load.

The bug in code

The whole CWE-400 class

A representative example of this vulnerability class. Not the vendor's source code; it shows the faulty pattern and its fix.

Vulnerable

1function expand(node) {
2  return node.children.map(expand);
3}

Fixed

1const MAX_DEPTH = 32;
2function expand(node, depth = 0) {
3  if (depth > MAX_DEPTH) throw new Error("too deep");
4  return node.children.map((c) => expand(c, depth + 1));
5}

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

Attack patterns (CAPEC)

ATT&CK techniques

Endpoint Denial of ServiceT1499

Change log

Fix✗ → ✓Sep 28, 2026, 10:11 PM UTC

For records you follow, these changes also arrive as notifications. →

References

kb.juniper.net/JSA11092

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records