How severe is CVE-2021-27647?

CVE-2021-27647 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-2021-27647 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 3% (86th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-27647?

CVE-2021-27647 affects Synology Diskstation Manager. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2021-27647?

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-2021-27647 published?

CVE-2021-27647 was published on 2021-03-12 and last updated on 2026-06-17.

CVE-2021-27647

CVE-2021-27647 is a critical-severity vulnerability in Synology Diskstation Manager 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-125.

Key facts

Severity: Critical (CVSS 3.x base score 9.8)
CVSS v2: 7.5
EPSS exploit prediction: 3% (86th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-125
Affected product: Synology Diskstation Manager
Published: 2021-03-12
Last modified: 2026-06-17

Description

Out-of-bounds Read vulnerability in iscsi_snapshot_comm_core in Synology DiskStation Manager (DSM) before 6.2.3-25426-3 allows remote attackers to execute arbitrary code via crafted web requests.

Frequently asked questions

What is CVE-2021-27647?: Out-of-bounds Read vulnerability in iscsi_snapshot_comm_core in Synology DiskStation Manager (DSM) before 6.2.3-25426-3 allows remote attackers to execute arbitrary code via crafted web requests.
How severe is CVE-2021-27647?: CVE-2021-27647 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-2021-27647 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 3% (86th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-27647?: CVE-2021-27647 affects Synology Diskstation Manager. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-27647?: 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-2021-27647 published?: CVE-2021-27647 was published on 2021-03-12 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:o:synology:diskstation_manager:*:*:*:*:*:*:*:*

More vulnerabilities in Synology Diskstation Manager

CVE-2022-27626 — Critical (CVSS 10.0): A vulnerability regarding concurrent execution using shared resource with improper synchronization ('Race Condition')…
CVE-2022-27625 — Critical (CVSS 10.0): A vulnerability regarding improper restriction of operations within the bounds of a memory buffer is found in the…
CVE-2022-27624 — Critical (CVSS 10.0): A vulnerability regarding improper restriction of operations within the bounds of a memory buffer is found in the…
CVE-2013-6955 — Critical (CVSS 10.0): webman/imageSelector.cgi in Synology DiskStation Manager (DSM) 4.0 before 4.0-2259, 4.2 before 4.2-3243, and 4.3 before…
CVE-2024-10441 — Critical (CVSS 9.8): Improper encoding or escaping of output vulnerability in the system plugin daemon in Synology BeeStation OS (BSM)…
CVE-2022-22687 — Critical (CVSS 9.8): Buffer copy without checking size of input ('Classic Buffer Overflow') vulnerability in Authentication functionality in…

All CVEs affecting Synology Diskstation Manager →

Other CWE-125 (Out-of-bounds Read) vulnerabilities

CVE-2026-24826 — Critical (CVSS 10.0): Out-of-bounds Write, Divide By Zero, NULL Pointer Dereference, Use of Uninitialized Resource, Out-of-bounds Read,…
CVE-2024-22004 — Critical (CVSS 10.0): Due to length check, an attacker with privilege access on a Linux Nonsecure operating system can trigger a…
CVE-2021-41556 — Critical (CVSS 10.0): sqclass.cpp in Squirrel through 2.2.5 and 3.x through 3.1 allows an out-of-bounds read (in the core interpreter) that…
CVE-2021-21777 — Critical (CVSS 10.0): An information disclosure vulnerability exists in the Ethernet/IP UDP handler functionality of EIP Stack Group OpENer…
CVE-2017-14451 — Critical (CVSS 10.0): An exploitable out-of-bounds read vulnerability exists in libevm (Ethereum Virtual Machine) of CPP-Ethereum. A…
CVE-2013-0767 — Critical (CVSS 10.0): The nsSVGPathElement::GetPathLengthScale function in Mozilla Firefox before 18.0, Firefox ESR 10.x before 10.0.12 and…

Browse all CWE-125 (Out-of-bounds Read) vulnerabilities →