How severe is CVE-2021-26563?

CVE-2021-26563 has a CVSS 3.x base score of 8.2, rated high severity. It is exploitable over local access with low attack complexity, requires high privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2021-26563 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (40th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-26563?

CVE-2021-26563 primarily affects Synology Diskstation Manager. In total, 4 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2021-26563?

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-2021-26563 published?

CVE-2021-26563 was published on 2021-02-26 and last updated on 2026-06-17.

CVE-2021-26563

CVE-2021-26563 is a high-severity vulnerability in Synology Diskstation Manager with a CVSS 3.x base score of 8.2. 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-863.

Key facts

Severity: High (CVSS 3.x base score 8.2)
CVSS v2: 4.6
EPSS exploit prediction: 1% (40th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-863
Affected product: Synology Diskstation Manager
Published: 2021-02-26
Last modified: 2026-06-17

Description

Incorrect authorization vulnerability in synoagentregisterd in Synology DiskStation Manager (DSM) before 6.2.4-25553 allows local users to execute arbitrary code via unspecified vectors.

Frequently asked questions

What is CVE-2021-26563?: Incorrect authorization vulnerability in synoagentregisterd in Synology DiskStation Manager (DSM) before 6.2.4-25553 allows local users to execute arbitrary code via unspecified vectors.
How severe is CVE-2021-26563?: CVE-2021-26563 has a CVSS 3.x base score of 8.2, rated high severity. It is exploitable over local access with low attack complexity, requires high privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2021-26563 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (40th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-26563?: CVE-2021-26563 primarily affects Synology Diskstation Manager. In total, 4 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2021-26563?: 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-2021-26563 published?: CVE-2021-26563 was published on 2021-02-26 and last updated on 2026-06-17.

References

Affected products (4)

cpe:2.3:o:synology:diskstation_manager:*:*:*:*:*:*:*:*
cpe:2.3:o:synology:vs960hd_firmware:-:*:*:*:*:*:*:*
cpe:2.3:o:synology:skynas_firmware:-:*:*:*:*:*:*:*
cpe:2.3:o:synology:diskstation_manager_unified_controller:3.0:*:*:*:*:*:*:*

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