How severe is CVE-2021-31349?

CVE-2021-31349 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2021-31349 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (77th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-31349?

CVE-2021-31349 affects Juniper 128 Technology Session Smart Router Firmware. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2021-31349?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.

When was CVE-2021-31349 published?

CVE-2021-31349 was published on 2021-10-19 and last updated on 2026-06-17.

CVE-2021-31349

CVE-2021-31349 is a critical-severity vulnerability in Juniper 128 Technology Session Smart Router Firmware with a CVSS 3.x base score of 9.8. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-287.

Key facts

Severity: Critical (CVSS 3.x base score 9.8)
CVSS v2: 7.5
EPSS exploit prediction: 2% (77th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-287
Affected product: Juniper 128 Technology Session Smart Router Firmware
Published: 2021-10-19
Last modified: 2026-06-17

Description

The usage of an internal HTTP header created an authentication bypass vulnerability (CWE-287), allowing an attacker to view internal files, change settings, manipulate services and execute arbitrary code. This issue affects all Juniper Networks 128 Technology Session Smart Router versions prior to 4.5.11, and all versions of 5.0 up to and including 5.0.1.

Frequently asked questions

What is CVE-2021-31349?: The usage of an internal HTTP header created an authentication bypass vulnerability (CWE-287), allowing an attacker to view internal files, change settings, manipulate services and execute arbitrary code. This issue affects all Juniper Networks 128 Technology Session Smart Router versions prior to 4.5.11, and all versions of 5.0 up to and including 5.0.1.
How severe is CVE-2021-31349?: CVE-2021-31349 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2021-31349 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (77th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-31349?: CVE-2021-31349 affects Juniper 128 Technology Session Smart Router Firmware. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-31349?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.
When was CVE-2021-31349 published?: CVE-2021-31349 was published on 2021-10-19 and last updated on 2026-06-17.

References

https://kb.juniper.net/JSA11256

Affected products (1)

cpe:2.3:o:juniper:128_technology_session_smart_router_firmware:*:*:*:*:*:*:*:*

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