MEDIUM
CVE-2021-26271
CWE-829Published: January 26, 2021· Updated: Jun 17, 2026
6.5
CVSS v3.1
Official Description
It was possible to execute a ReDoS-type attack inside CKEditor 4 before 4.16 by persuading a victim to paste crafted text into the Styles input of specific dialogs (in the Advanced Tab for Dialogs plugin).
Technical Analysis
CVE-2021-26271 can be exploited remotely over the network without requiring physical or adjacent access, significantly expanding the attack surface for threat actors.
Exploitation does not require any privileges, though user interaction (Required) is needed, which slightly reduces the risk of mass automated attacks.
A successful exploit results in availability disruption (denial of service), with a CVSS base score of 6.5.
CVSS v3.1 Vector Breakdown
Exploitability
Attack VectorNetwork
Attack ComplexityLow
Privileges Req.None
User InteractionRequired
ScopeUnchanged
Impact
ConfidentialityNone
IntegrityNone
AvailabilityHigh
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H
Affected Vendors & Products
Exploit & PoC Resources
NO KNOWN EXPLOITNo public exploit confirmed at this time
Exploit-DB
Offensive Security exploit database
GitHub PoC Search
Community PoC repositories
Rapid7 / Metasploit
Metasploit module search
PacketStorm
Security advisories & exploits
NVD Detail
Official NIST entry
MITRE CVE
CVE Program entry
External links open in a new tab. Always verify in a controlled environment before use.
Official Patches & Advisories
All References (8)
→
→
https://github.com/ckeditor/ckeditor4/blob/major/CHANGES.md#ckeditor-416Release Notes · Third Party Advisory
→
https://www.oracle.com//security-alerts/cpujul2021.htmlPatch · Third Party Advisory
→
https://www.oracle.com/security-alerts/cpuoct2021.htmlPatch · Third Party Advisory
→
→
https://github.com/ckeditor/ckeditor4/blob/major/CHANGES.md#ckeditor-416Release Notes · Third Party Advisory
→
https://www.oracle.com//security-alerts/cpujul2021.htmlPatch · Third Party Advisory
→
https://www.oracle.com/security-alerts/cpuoct2021.htmlPatch · Third Party Advisory
Quick Facts
CVE IDCVE-2021-26271
CVSS Score6.5 / 10
SeverityMEDIUM
WeaknessCWE-829
CISA KEVNo
Affected2 vendor(s)
PublishedJan 26, 2021
Related CVEs (CWE-829)
Recommended Actions
- →Apply vendor patches immediately
- →Monitor CVE-2021-26271 in threat intel feeds
- →Review IDS/IPS signatures for exploitation attempts
Data sourced from NVD (NIST), CISA KEV, and EPSS (FIRST). Analysis generated by CTIWatch. CVE data is provided under the NVD usage policy.