CVE-2021-26102: A relative path traversal vulnerability (CWE-23) in FortiWAN version 4.5.7 and below, 4.4 all versions may all

This week

CRITICAL 9.8REMOTEUPGRADE

CVE-2021-26102 is a critical-severity flaw (CVSS 9.8) affecting fortiwan. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

A relative path traversal vulnerability (CWE-23) in FortiWAN version 4.5.7 and below, 4.4 all versions may allow a remote non-authenticated attacker to delete files on the system by sending a crafted POST request. In particular, deleting specific configuration files will reset the Admin password to its default value.

Why this priority

Critical severity
EPSS top 3%: very likely to be exploited
Public exploit reference
CISA SSVC: automatable with total technical impact
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	9.8 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	19.7% (top 3%)
CISA exploited list	No
Weakness	CWE-305, CWE-22
Published	2024-12-19
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

2024-12-19 14:15 UTCPublished CVE record published
2026-06-17 03:42 UTCUpdated Record last modified

fortinet fortiwan UPGRADE

Affected: >= 4.4.0 and < 4.5.8

Fixed in: 4.5.8

Safe to downgrade to: a release before 4.4.0

1. Check installed version

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

2. UPGRADE to 4.5.8 (Debian / Ubuntu)

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

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade fortiwan

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 4.4.0 (Debian / Ubuntu)

apt-cache madison fortiwan sudo apt install fortiwan=<VERSION_BEFORE_4.4.0> sudo apt-mark hold fortiwan

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

dnf --showduplicates list fortiwan sudo dnf downgrade fortiwan-<VERSION_BEFORE_4.4.0> sudo dnf versionlock add fortiwan

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.

Exact fixes by distribution

Fedora 46 · byobu · FIXED · 7.23-1.fc46 · FEDORA-2026-08f2b53446 · source

sudo dnf upgrade --advisory=FEDORA-2026-08f2b53446

Public exploits and detection

Public code exists for this CVE. Treat unpatched systems as at risk, and only run PoCs in a lab.

GitHub PoC: SleepyCofe/CVE-2021-26102 (8 stars)

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-2021-26102?

fortiwan: upgrade to 4.5.8. Exact commands for each OS are on this page.

Is CVE-2021-26102 being exploited?

CVE-2021-26102 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-2021-26102 affect?

CVE-2021-26102 affects fortiwan. Severity is critical (CVSS 9.8). A relative path traversal vulnerability (CWE-23) in FortiWAN version 4.5.7 and below, 4.4 all versions may allow a remote non-authenticated attacker to delete files on the system by sending a crafted POST request. In particular, deleting sp

How urgent is CVE-2021-26102?

Priority 72/100. Critical severity; EPSS top 3%: very likely to be exploited; Public exploit reference; CISA SSVC: automatable with total technical impact; Remotely exploitable, no login, no user action

Software pages

Fortinet vulnerabilities

Related CVEs

CVE-2021-26115 HIGH 7.8 UPGRADE An OS command injection (CWE-78) vulnerability in FortiWAN version 4.5.7 and below Command Line Interface may

References

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