PatchTheCVECVE-2021-26271: It was possible to execute a ReDoS-type attack inside CKEditor 4 before 4.16 by persuading a victim to paste c
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MEDIUM 6.5UPGRADEDOWNGRADEUPGRADE
CVE-2021-26271 is a medium-severity flaw (CVSS 6.5) affecting ckeditor, agile product lifecycle management, application express. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.
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).
Why this priority
- No elevated risk signals yet
A fixed release or distro patch exists.
Risk facts
| CVSS score | 6.5 (Medium) |
| Attack vector | Network (remote) |
| Attack complexity | Low |
| Privileges needed | None |
| User interaction | Required |
| EPSS exploit chance | 2.0% (top 19%) |
| CISA exploited list | No |
| Weakness | CWE-829 |
| Published | 2021-01-26 |
| Last modified | 2026-08-25 |
Last updated 2026-08-25 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score
Am I affected?
Timeline
- Published CVE record published
- Updated Record last modified
ckeditor ckeditor UPGRADE
Affected: >= 4.0 and < 4.16
Fixed in: 4.16
Safe to downgrade to: a release before 4.0
1. Check installed version
apt-cache policy ckeditor || rpm -q ckeditor || ckeditor --version
2. UPGRADE to 4.16 (Debian / Ubuntu)
sudo apt update && sudo apt install --only-upgrade ckeditor
2. UPGRADE (RHEL / Amazon Linux / Fedora)
sudo dnf upgrade ckeditor
Note
Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.
3. If no update is available yet, DOWNGRADE to a release before 4.0 (Debian / Ubuntu)
apt-cache madison ckeditor
sudo apt install ckeditor=<VERSION_BEFORE_4.0>
sudo apt-mark hold ckeditor
3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)
dnf --showduplicates list ckeditor
sudo dnf downgrade ckeditor-<VERSION_BEFORE_4.0>
sudo dnf versionlock add ckeditor
Downgrade risk
Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.
After downgrade
Restart the service, and keep the package held until a fixed release ships.
oracle agile product lifecycle management DOWNGRADE
Affected: 9.3.5 · 9.3.6
Fixed in: no fixed release known
Safe to downgrade to: a release before 9.3.5
1. Check installed version
apt-cache policy agile-product-lifecycle-management || rpm -q agile-product-lifecycle-management || agile-product-lifecycle-management --version
2. No fixed release: DOWNGRADE to a release before 9.3.5 (Debian / Ubuntu)
apt-cache madison agile-product-lifecycle-management
sudo apt install agile-product-lifecycle-management=<VERSION_BEFORE_9.3.5>
sudo apt-mark hold agile-product-lifecycle-management
2. No fixed release: DOWNGRADE (RHEL / Amazon Linux / Fedora)
dnf --showduplicates list agile-product-lifecycle-management
sudo dnf downgrade agile-product-lifecycle-management-<VERSION_BEFORE_9.3.5>
sudo dnf versionlock add agile-product-lifecycle-management
Downgrade risk
Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.
After downgrade
Restart the service, and keep the package held until a fixed release ships.
oracle application express UPGRADE
Affected: < 21.1.0
Fixed in: 21.1.0
Safe to downgrade to: no unaffected older release
1. Check installed version
apt-cache policy application-express || rpm -q application-express || application-express --version
2. UPGRADE to 21.1.0 (Debian / Ubuntu)
sudo apt update && sudo apt install --only-upgrade application-express
2. UPGRADE (RHEL / Amazon Linux / Fedora)
sudo dnf upgrade application-express
Note
Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.
oracle financial services analytical applications infrastructure UPGRADE
Affected: >= 8.0.6 and <= 8.0.9 · 8.1.0 · 8.1.1
Fixed in: newer than 8.0.9
Safe to downgrade to: a release before 8.0.6
1. Check installed version
apt-cache policy financial-services-analytical-applications-infrastructure || rpm -q financial-services-analytical-applications-infrastructure || financial-services-analytical-applications-infrastructure --version
2. UPGRADE to newer than 8.0.9 (Debian / Ubuntu)
sudo apt update && sudo apt install --only-upgrade financial-services-analytical-applications-infrastructure
2. UPGRADE (RHEL / Amazon Linux / Fedora)
sudo dnf upgrade financial-services-analytical-applications-infrastructure
Note
Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.
3. If no update is available yet, DOWNGRADE to a release before 8.0.6 (Debian / Ubuntu)
apt-cache madison financial-services-analytical-applications-infrastructure
sudo apt install financial-services-analytical-applications-infrastructure=<VERSION_BEFORE_8.0.6>
sudo apt-mark hold financial-services-analytical-applications-infrastructure
3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)
dnf --showduplicates list financial-services-analytical-applications-infrastructure
sudo dnf downgrade financial-services-analytical-applications-infrastructure-<VERSION_BEFORE_8.0.6>
sudo dnf versionlock add financial-services-analytical-applications-infrastructure
Downgrade risk
Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.
After downgrade
Restart the service, and keep the package held until a fixed release ships.
oracle jd edwards enterpriseone tools UPGRADE
Affected: < 9.2.6.0
Fixed in: 9.2.6.0
Safe to downgrade to: no unaffected older release
1. Check installed version
apt-cache policy jd-edwards-enterpriseone-tools || rpm -q jd-edwards-enterpriseone-tools || jd-edwards-enterpriseone-tools --version
2. UPGRADE to 9.2.6.0 (Debian / Ubuntu)
sudo apt update && sudo apt install --only-upgrade jd-edwards-enterpriseone-tools
2. UPGRADE (RHEL / Amazon Linux / Fedora)
sudo dnf upgrade jd-edwards-enterpriseone-tools
Note
Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.
oracle siebel ui framework UPGRADE
Affected: < 21.9
Fixed in: 21.9
Safe to downgrade to: no unaffected older release
1. Check installed version
apt-cache policy siebel-ui-framework || rpm -q siebel-ui-framework || siebel-ui-framework --version
2. UPGRADE to 21.9 (Debian / Ubuntu)
sudo apt update && sudo apt install --only-upgrade siebel-ui-framework
2. UPGRADE (RHEL / Amazon Linux / Fedora)
sudo dnf upgrade siebel-ui-framework
Note
Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.
Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.
Quick answers
How do I fix CVE-2021-26271?
ckeditor: upgrade to 4.16; agile product lifecycle management: downgrade or apply the listed mitigation; application express: upgrade to 21.1.0. Exact commands for each OS are on this page.
Is CVE-2021-26271 being exploited?
CVE-2021-26271 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.
What does CVE-2021-26271 affect?
CVE-2021-26271 affects ckeditor, agile product lifecycle management, application express. Severity is medium (CVSS 6.5). 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).
How urgent is CVE-2021-26271?
Priority 43/100. No elevated risk signals yet.
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