CVE-2026-40688: An out-of-bounds write vulnerability [CWE-787] vulnerability in Fortinet FortiWeb 8.0.0 through 8.0.3, FortiWe

This month

HIGH 7.2UPGRADE

CVE-2026-40688 is a high-severity flaw (CVSS 7.2) affecting fortiweb. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

An out-of-bounds write vulnerability [CWE-787] vulnerability in Fortinet FortiWeb 8.0.0 through 8.0.3, FortiWeb 7.6.0 through 7.6.6, FortiWeb 7.4.0 through 7.4.11 may allow a remote privileged attacker to execute arbitrary code or command via crafted HTTP requests.

Why this priority

High severity
EPSS top 6%: very likely to be exploited

A fixed release or distro patch exists.

Risk facts

CVSS score	7.2 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	High
User interaction	None
EPSS exploit chance	6.4% (top 6%)
CISA exploited list	No
Weakness	CWE-787
Published	2026-04-14
Last modified	2026-07-24

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

Last updated 2026-07-24 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-04-14 23:16 UTCPublished CVE record published
2026-07-24 21:10 UTCUpdated Record last modified

fortinet fortiweb UPGRADE

Affected: >= 7.4.0 and < 7.4.12 · >= 7.6.0 and < 7.6.7 · >= 8.0.0 and < 8.0.4

Fixed in: 7.4.12, 7.6.7, 8.0.4

Safe to downgrade to: a release before 7.4.0

1. Check installed version

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

2. UPGRADE to 7.4.12 (Debian / Ubuntu)

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

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade fortiweb

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 7.4.0 (Debian / Ubuntu)

apt-cache madison fortiweb sudo apt install fortiweb=<VERSION_BEFORE_7.4.0> sudo apt-mark hold fortiweb

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

dnf --showduplicates list fortiweb sudo dnf downgrade fortiweb-<VERSION_BEFORE_7.4.0> sudo dnf versionlock add fortiweb

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-2026-40688?

fortiweb: upgrade to 7.4.12, 7.6.7, 8.0.4. Exact commands for each OS are on this page.

Is CVE-2026-40688 being exploited?

CVE-2026-40688 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-2026-40688 affect?

CVE-2026-40688 affects fortiweb. Severity is high (CVSS 7.2). An out-of-bounds write vulnerability [CWE-787] vulnerability in Fortinet FortiWeb 8.0.0 through 8.0.3, FortiWeb 7.6.0 through 7.6.6, FortiWeb 7.4.0 through 7.4.11 may allow a remote privileged attacker to execute arbitrary code or command v

How urgent is CVE-2026-40688?

Priority 49/100. High severity; EPSS top 6%: very likely to be exploited

Software pages

Fortinet vulnerabilities

Related CVEs

CVE-2026-39811 MEDIUM 4.9 UPGRADE A integer overflow or wraparound vulnerability in Fortinet FortiWeb 8.0.0 through 8.0.3, FortiWeb 7.6.0 throug
CVE-2026-39814 MEDIUM 6.7 UPGRADE A relative path traversal vulnerability in Fortinet FortiWeb 8.0.0 through 8.0.2, FortiWeb 7.6.0 through 7.6.6
CVE-2026-70466 MEDIUM 5.3 UPGRADE A incomplete list of disallowed inputs vulnerability in Fortinet FortiWeb 8.0.0 through 8.0.2, FortiWeb 7.6.0
CVE-2026-26035 CRITICAL 9.8 UPGRADE An Improper Authentication vulnerability [CWE-287] vulnerability in Fortinet FortiWeb 8.0.0 through 8.0.2, For

References

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