⚠ Reference material — not professional advice. Test in staging, back up first, verify against your specific version. Use your own judgment for your environment.
● Critical · CVSS 9.2 ⚠ ACTIVELY EXPLOITED — CISA KEV

How to Fix CVE-2023-27997: Path Traversal in FortiOS-6K7K

Other vulnerabilities in the same area that are worth patching alongside this one:

*By Sai Kiran Pandrala*

⚡ At a glance
SeverityCVSS 9.2 - Critical
Actively exploited?Yes, listed in CISA KEV (added 2023-06-13)
Affected7.0.10, 7.0.5, 6.4.12, 6.4.10, 6.4.8, 6.4.6, and others
Fixed inSee vendor advisory
Type (CWE)CWE-122: Execute unauthorized code or commands
Patch immediately. CISA's KEV listing means active exploitation is confirmed. Federal agencies must remediate by 2023-07-04.

What is CVE-2023-27997?

CVE-2023-27997 is a path traversal flaw in FortiOS-6K7K. The product fails to canonicalize or restrict file paths supplied by a remote caller, so .. sequences or absolute paths reach restricted parts of the filesystem. Vendor description: A heap-based buffer overflow vulnerability [CWE-122] in FortiOS version 7.2.4 and below, version 7.0.11 and below, version 6.4.12 and below, version 6.0.16 and below and FortiProxy version 7.2.3 and below, version 7.0.9 and below, version 2.0.12 and below, version 1.2 all versions, version 1.1 all versions SSL-VPN may allow a remote attacker to execute arbitrary code or commands via specifically crafted requests.

Why this CVE matters

Path traversal flaws look low-impact on paper but routinely chain into full compromise. An attacker who can read arbitrary files often pulls configuration secrets, session databases, or private keys, and many traversal bugs also allow writes that drop a webshell into the document root.

For deployments of FortiOS-6K7K that have been exposed to the public internet during the disclosure window, the operating assumption should be that scanning has already happened. Confirmed in-the-wild exploitation makes that assumption mandatory, not cautious. Patching closes the door; log review and credential rotation close out the rest of the response.

Am I affected?

You are affected if your installation matches any of these version ranges:

Check your installed version against the list above. If you cannot determine the version, treat the system as affected and follow the upgrade path below.

On FortiGate / FortiOS systems, run get system status from the CLI and compare the Version line against the affected ranges above.

How to fix CVE-2023-27997

  1. Read the vendor advisory in full: https://fortiguard.com/psirt/FG-IR-23-097
  2. Upgrade FortiOS-6K7K to the patched build listed in the vendor advisory.
  3. Back up the configuration (and database, where applicable) before upgrading.
  4. Apply the patch in a maintenance window. For HA pairs, upgrade the standby node first, fail over, then upgrade the former primary.
  5. Restart the affected service so the patched binary loads, then verify the new version (see verification section).

Apply the iOS / iPadOS update


# Check the current iOS build on a tethered device (libimobiledevice)
ideviceinfo -k ProductVersion
ideviceinfo -k BuildVersion

# Required iOS / iPadOS build is listed in the vendor advisory: https://fortiguard.com/psirt/FG-IR-23-097
# On-device: Settings -> General -> Software Update -> Download and Install


# Vendor advisory: https://fortiguard.com/psirt/FG-IR-23-097
# Confirm fleet iOS devices have updated (Intune example)
Connect-MgGraph -Scopes Device.Read.All
Get-MgDeviceManagementManagedDevice -Filter "operatingSystem eq 'iOS'" |
  Where-Object { $_.OSVersion -lt "<fixed-version-from-advisory>" } |
  Select-Object DeviceName, OSVersion, UserPrincipalName

Verify the fix landed


# 1. Confirm the running version matches the fixed-in version from the advisory:
#    https://fortiguard.com/psirt/FG-IR-23-097
#    Use the platform-specific version probe above.

# 2. Re-scan with your vulnerability scanner (Nessus, Qualys, Tenable, OpenVAS).
#    The scanner should no longer flag CVE-2023-27997 on the patched target.

# 3. Inspect recent service / kernel logs for crash loops or rollback events.
journalctl -u <service> --since "10 minutes ago"
dmesg --since "10 minutes ago"

If you cannot patch immediately

Block requests containing ../, ..%2f, or absolute path prefixes at a reverse proxy. Restrict access to the affected endpoint to trusted networks. Apply the patched build as the real fix.

How to verify the fix worked

If your installation was internet-reachable during the disclosure window, treat log review as part of the remediation rather than an optional follow-up. Look for unusually long URI paths containing traversal sequences, unexpectedly large responses from the affected endpoint, and outbound requests from the application to internal addresses or cloud-metadata endpoints. Treat any sensitive file the bug could disclose as exposed. Because FortiOS-6K7K sits on CISA's Known Exploited Vulnerabilities catalog for this CVE, defenders should also pull the IOC list from the vendor advisory and from CISA's analysis if one was published.

Frequently asked questions

Is CVE-2023-27997 being exploited in the wild?

Yes. CISA added CVE-2023-27997 to the Known Exploited Vulnerabilities catalog, which means active exploitation has been confirmed by federal observation or credible vendor reporting.

Will a WAF or IDS rule fully mitigate CVE-2023-27997?

No. Network-layer filters can reduce noise and slow opportunistic scanners, but they will not stop a determined attacker. The vendor patch is the only durable fix.

How long should I plan for the upgrade?

Typical vendor-documented upgrade windows for FortiOS-6K7K run from a few minutes to under an hour depending on cluster size. Test in a staging environment first and follow the vendor's documented HA upgrade order.

References

*This guide was assembled from the official vendor advisory, the NVD record, and the CISA KEV catalog entry on 2026-05-25. Always confirm against the vendor advisory before applying changes in production.*