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CVE-2021-31361

20
FAUCET Score

CVE-2021-31361 is a Denial of Service (DoS) vulnerability in Juniper Networks Junos OS affecting QFX and PTX Series devices. An unauthenticated attacker can exploit improper handling of exceptional conditions by sending specific VXLAN-encapsulated IP packets, leading to increased FPC CPU utilization and a sustained DoS. This vulnerability has a CVSS score of 5.3 (Medium), indicating a low attack complexity and no user interaction required. The primary impact is a loss of availability due to the sustained DoS condition. Currently, there is no evidence of active exploitation, public exploit code (Metasploit, Nuclei, ExploitDB), or significant community discussion or media coverage surrounding this CVE.

Impacted Technologies

VendorProductVersion(s)CPE
< 18.4R3-S9CPE match
cpe:2.3:o:juniper:junos:*:*:*:*:*:*:*:*
>= 19.1, < 19.1R3-S6CPE match
cpe:2.3:o:juniper:junos:*:*:*:*:*:*:*:*
>= 20.2, < 20.2R3-S1CPE match
cpe:2.3:o:juniper:junos:*:*:*:*:*:*:*:*
< 17.3R3-S11CPE match
cpe:2.3:o:juniper:junos:*:*:*:*:*:*:*:*
>= 18.1, < 18.1R3-S12CPE match
cpe:2.3:o:juniper:junos:*:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

5.3MEDIUM

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

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
NONE
Integrity Impact
NONE
Availability Impact
LOW
Exploitability Score
3.9
Impact Score
1.4
CvssVersion
3.1

Exploit Intelligence

EPSS Score
1.01%
Probability of exploitation in next 30 days
EPSS Percentile
59.7%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.0101 is in the 37th percentile among its peer group of 23,705 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.0 Reddit, 0.1 Bluesky, 0.0 Mastodon, and 0.4 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.0 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Patch Available

Vendor Patches (1)

juniperpatch availablevia nvd_reference
View patch

References

kb.juniper.net / JSA11223
PatchVendor Advisory