CVE-2026-39811: A integer overflow or wraparound vulnerability in Fortinet FortiWeb 8.0.0 through 8.0.3, FortiWeb 7.6.0 throug

Routine

MEDIUM 4.9UPGRADE

CVE-2026-39811 is a medium-severity flaw (CVSS 4.9) affecting fortiweb. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

A integer overflow or wraparound vulnerability in Fortinet FortiWeb 8.0.0 through 8.0.3, FortiWeb 7.6.0 through 7.6.6, FortiWeb 7.4 all versions, FortiWeb 7.2 all versions, FortiWeb 7.0 all versions may allow attacker to denial of service via <insert attack vector here>

Why this priority

No elevated risk signals yet

A fixed release or distro patch exists.

Risk facts

CVSS score	4.9 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	High
User interaction	None
EPSS exploit chance	0.4% (top 70%)
CISA exploited list	No
Weakness	CWE-190
Published	2026-04-14
Last modified	2026-10-26

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

Last updated 2026-10-26 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-04-14 16:16 UTCPublished CVE record published
2026-10-26 21:10 UTCUpdated Record last modified

fortinet fortiweb UPGRADE

Affected: >= 7.0.0 and <= 7.0.13 · >= 7.2.0 and <= 7.2.13 · >= 7.4.0 and <= 7.4.12 · >= 7.6.0 and < 7.6.7 · >= 8.0.0 and < 8.0.4

Fixed in: 7.6.7, 8.0.4

Safe to downgrade to: a release before 7.0.0

1. Check installed version

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

2. UPGRADE to 7.6.7 (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 7.0.0 (Debian / Ubuntu)

apt-cache madison fortiweb sudo apt install fortiweb=<VERSION_BEFORE_7.0.0> 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_7.0.0> 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-2026-39811?

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

Is CVE-2026-39811 being exploited?

CVE-2026-39811 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-2026-39811 affect?

CVE-2026-39811 affects fortiweb. Severity is medium (CVSS 4.9). A integer overflow or wraparound vulnerability in Fortinet FortiWeb 8.0.0 through 8.0.3, FortiWeb 7.6.0 through 7.6.6, FortiWeb 7.4 all versions, FortiWeb 7.2 all versions, FortiWeb 7.0 all versions may allow attacker to denial of service v

How urgent is CVE-2026-39811?

Priority 25/100. No elevated risk signals yet.

Software pages

Fortinet vulnerabilities

Related CVEs

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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