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Fencer Intel
critical 9.8

CVE-2021-25830 in the critical feed json

A file extension handling issue was found in [core] module of ONLYOFFICE DocumentServer v4.2.0.236-v5.6.4.13.

published 5y ago modified 4mo ago also EUVD-2021-12713

cvss
9.8
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
11.8%
EPSS 11.8% chance of exploitation in 30 days, percentile 96%
public exploits
0
none known

Summary

A file extension handling issue was found in [core] module of ONLYOFFICE DocumentServer v4.2.0.236-v5.6.4.13. An attacker must request the conversion of the crafted file from DOCT into DOCX format. Using the chain of two other bugs related to improper string handling, an attacker can achieve remote code execution on DocumentServer.

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Exploit prediction

11.76% chance of exploitation in the next 30 days, higher than 96% of all scored CVEs (FIRST EPSS, 2026-11-09).

Exploits and checks

  • github.com https://github.com/merrychap/poc_exploits/tree/master/ONLYOFFICE/CVE-2021-25830 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
NVD 3.1 9.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
NVD 2.0 7.5 AV:N/AC:L/Au:N/C:P/I:P/A:P

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.