CVE-2021-26271

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).

Published: 2021-01-26 Last update: 2024-11-21 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2021-26271 is rated Moderate Risk (50.5/100): CVSS Medium severity, with medium exploitation likelihood (EPSS 0.62%). Review affected assets and schedule remediation.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2021-26271

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-02-25 0.43% 0.62% +0.19%
2 2025-12-14 0.64% 0.43% -0.21%
3 2025-11-21 — 0.64% —

Full EPSS history (18 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2021-26271

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
6.5 3.1 MEDIUM
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:R)
A real person has to do something—click, install, enable—otherwise it doesn’t land.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 2.8 3.6 [email protected]
4.3 2.0 MEDIUM
AV:N/AC:M/Au:N/C:N/I:N/A:P Click to expand
Access vector (AV:N)
Can be exploited remotely over network reachability.
Access complexity (AC:M)
Exploitation needs some favorable conditions, but not exceptional ones.
Authentication (AU:N)
No authentication is required.
Confidentiality impact (C:N)
No confidentiality impact.
Integrity impact (I:N)
No integrity impact.
Availability impact (A:P)
Partial availability impact.
 8.6 2.9 [email protected]

Weakness enumeration for CVE-2021-26271

GitHub Security Advisory for CVE-2021-26271

OS Trackers for CVE-2021-26271

vendor priority summary link
debian unimportant CVE-2021-26271 unimportant priority: Debian including 2 source packages (ckeditor, ckeditor3), 4 status rows across 2 suites (bookworm, bullseye): resolved 4. https://security-tracker.debian.org/tracker/CVE-2021-26271
ubuntu medium CVE-2021-26271 medium priority: Ubuntu including 1 source packages (ckeditor), 16 status rows across 16 suites (bionic, focal, groovy, hirsute, impish, jammy, kinetic, lunar, mantic, noble, oracular, plucky, questing, trusty, upstream, xenial): not-affected 8, needs-triage 3, ignored 2, released 2, DNE 1. https://ubuntu.com/security/CVE-2021-26271

Affected software / configurations for CVE-2021-26271

Vendor Product Version Raw CPE
ckeditor ckeditor >= 4.0, < 4.16 cpe:2.3:a:ckeditor:ckeditor:*:*:*:*:*:*:*:*
oracle agile_plm 9.3.5 cpe:2.3:a:oracle:agile_plm:9.3.5:*:*:*:*:*:*:*
oracle agile_plm 9.3.6 cpe:2.3:a:oracle:agile_plm:9.3.6:*:*:*:*:*:*:*
oracle application_express < 21.1.0 cpe:2.3:a:oracle:application_express:*:*:*:*:*:*:*:*
oracle financial_services_analytical_applications_infrastructure >= 8.0.6, <= 8.0.9 cpe:2.3:a:oracle:financial_services_analytical_applications_infrastructure:*:*:*:*:*:*:*:*
oracle financial_services_analytical_applications_infrastructure 8.1.0 cpe:2.3:a:oracle:financial_services_analytical_applications_infrastructure:8.1.0:*:*:*:*:*:*:*
oracle financial_services_analytical_applications_infrastructure 8.1.1 cpe:2.3:a:oracle:financial_services_analytical_applications_infrastructure:8.1.1:*:*:*:*:*:*:*
oracle jd_edwards_enterpriseone_tools < 9.2.6.0 cpe:2.3:a:oracle:jd_edwards_enterpriseone_tools:*:*:*:*:*:*:*:*
oracle siebel_ui_framework < 21.9 cpe:2.3:a:oracle:siebel_ui_framework:*:*:*:*:*:*:*:*
oracle webcenter_sites 12.2.1.3.0 cpe:2.3:a:oracle:webcenter_sites:12.2.1.3.0:*:*:*:*:*:*:*
oracle webcenter_sites 12.2.1.4.0 cpe:2.3:a:oracle:webcenter_sites:12.2.1.4.0:*:*:*:*:*:*:*

References for CVE-2021-26271

cvelogic Threat Intelligence