CVE-2021-26087: An improper neutralization of input during web page generation in FortiWLC version 8.6.0, version 8.5.3 and be

Routine

MEDIUM 4.3UPGRADE

CVE-2021-26087 is a medium-severity flaw (CVSS 4.3) affecting fortiwlc. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

An improper neutralization of input during web page generation in FortiWLC version 8.6.0, version 8.5.3 and below, version 8.4.8 and below, version 8.3.3 web interface may allow both authenticated remote attackers and non-authenticated attackers in the same network as the appliance to perform a stored cross site scripting attack (XSS) via injecting malicious payloads in different locations.

Why this priority

No elevated risk signals yet

A fixed release or distro patch exists.

Risk facts

CVSS score	4.3 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	Low
User interaction	None
EPSS exploit chance	0.3% (top 73%)
CISA exploited list	No
Weakness	CWE-79
Published	2025-03-17
Last modified	2026-06-17

Publisher (CNA): Fortinet, Inc. · Vendor: fortinet

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2025-03-17 14:15 UTCPublished CVE record published
2026-06-17 03:42 UTCUpdated Record last modified

fortinet fortiwlc UPGRADE

Affected: >= 8.4.0 and <= 8.4.2 · >= 8.4.4 and < 8.5.4 · 8.3.3 · 8.6.0

Fixed in: 8.5.4

Safe to downgrade to: a release before 8.3.3

1. Check installed version

apt-cache policy fortiwlc || rpm -q fortiwlc || fortiwlc --version

2. UPGRADE to 8.5.4 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade fortiwlc

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade fortiwlc

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 8.3.3 (Debian / Ubuntu)

apt-cache madison fortiwlc sudo apt install fortiwlc=<VERSION_BEFORE_8.3.3> sudo apt-mark hold fortiwlc

3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list fortiwlc sudo dnf downgrade fortiwlc-<VERSION_BEFORE_8.3.3> sudo dnf versionlock add fortiwlc

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.

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.

Quick answers

How do I fix CVE-2021-26087?

fortiwlc: upgrade to 8.5.4. Exact commands for each OS are on this page.

Is CVE-2021-26087 being exploited?

CVE-2021-26087 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-2021-26087 affect?

CVE-2021-26087 affects fortiwlc. Severity is medium (CVSS 4.3). An improper neutralization of input during web page generation in FortiWLC version 8.6.0, version 8.5.3 and below, version 8.4.8 and below, version 8.3.3 web interface may allow both authenticated remote attackers and non-authenticated atta

How urgent is CVE-2021-26087?

Priority 22/100. No elevated risk signals yet.

Software pages

Fortinet vulnerabilities

Related CVEs

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References

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