How severe is CVE-2021-35309?

CVE-2021-35309 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over an adjacent network with high attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2021-35309 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (36th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-35309?

CVE-2021-35309 affects Samsung Syncthru Web Service. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2021-35309?

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

When was CVE-2021-35309 published?

CVE-2021-35309 was published on 2023-08-22 and last updated on 2026-06-17.

CVE-2021-35309

CVE-2021-35309 is a high-severity vulnerability in Samsung Syncthru Web Service with a CVSS 3.x base score of 7.5. 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-269.

Key facts

Severity: High (CVSS 3.x base score 7.5)
EPSS exploit prediction: 0% (36th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-269
Affected product: Samsung Syncthru Web Service
Published: 2023-08-22
Last modified: 2026-06-17

Description

An issue discovered in Samsung SyncThru Web Service SPL 5.93 06-09-2014 allows attackers to gain escalated privileges via MITM attacks.

Frequently asked questions

What is CVE-2021-35309?: An issue discovered in Samsung SyncThru Web Service SPL 5.93 06-09-2014 allows attackers to gain escalated privileges via MITM attacks.
How severe is CVE-2021-35309?: CVE-2021-35309 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over an adjacent network with high attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2021-35309 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (36th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-35309?: CVE-2021-35309 affects Samsung Syncthru Web Service. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-35309?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
When was CVE-2021-35309 published?: CVE-2021-35309 was published on 2023-08-22 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:samsung:syncthru_web_service:5.93:*:*:*:*:*:*:*

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