How severe is CVE-2021-25829?

CVE-2021-25829 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.

Is CVE-2021-25829 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 7% (94th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-25829?

CVE-2021-25829 affects Onlyoffice Document Server. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2021-25829?

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-2021-25829 published?

CVE-2021-25829 was published on 2021-03-01 and last updated on 2026-06-17.

CVE-2021-25829

CVE-2021-25829 is a high-severity vulnerability in Onlyoffice Document Server 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.

Key facts

Severity: High (CVSS 3.x base score 7.5)
CVSS v2: 7.8
EPSS exploit prediction: 7% (94th percentile)
Actively exploited: Not listed in CISA KEV
Affected product: Onlyoffice Document Server
Published: 2021-03-01
Last modified: 2026-06-17

Description

An improper binary stream data handling issue was found in the [core] module of ONLYOFFICE DocumentServer v4.0.0-9-v5.6.3. Using this bug, an attacker is able to produce a denial of service attack that can eventually shut down the target server.

Frequently asked questions

What is CVE-2021-25829?: An improper binary stream data handling issue was found in the [core] module of ONLYOFFICE DocumentServer v4.0.0-9-v5.6.3. Using this bug, an attacker is able to produce a denial of service attack that can eventually shut down the target server.
How severe is CVE-2021-25829?: CVE-2021-25829 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.
Is CVE-2021-25829 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 7% (94th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-25829?: CVE-2021-25829 affects Onlyoffice Document Server. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-25829?: 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-2021-25829 published?: CVE-2021-25829 was published on 2021-03-01 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:onlyoffice:document_server:*:*:*:*:*:*:*:*