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Out-of-bounds write in FortiOS CAPWAP daemon

IdentifiersCVE-2025-53844CWE-787· Out-of-bounds Write

CVE-2025-53844 is an out-of-bounds write vulnerability in the CAPWAP daemon of Fortinet FortiOS. It affects FortiOS 7.6.0 through 7.6.3, 7.4.0 through 7.4.8, and 7.2.0 through 7.2.11. The flaw can be triggered with specially crafted or malformed CAPWAP packets, causing memory corruption in the CAPWAP-handling process. Available reporting indicates exploitation requires an attacker to control an access point endpoint or other authenticated CAPWAP-connected device, such as a FortiAP, FortiExtender, or FortiSwitch, and then send malicious CAPWAP traffic to the FortiGate/FortiOS device. The vulnerability is tracked by Fortinet as FG-IR-26-123.

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ANALYST BRIEF

Impact, mitigation & remediation

What it means. What to do now. Patch path, mitigations, and the assume-compromise checklist.

Impact

What an attacker gets, and what they’ve been doing with it.

Successful exploitation can crash the vulnerable CAPWAP/FortiOS process or compromise it, and may allow execution of unauthorized code or commands on the affected FortiGate device. In practical terms, this can result in denial of service of the CAPWAP-related service and potentially full process compromise with attacker-controlled execution on the appliance.

Mitigation

If you can’t patch tonight, do this now.

Until patched, reduce exposure of the CAPWAP daemon to only trusted managed endpoints, restrict or tightly control CAPWAP-connected devices, and investigate for rogue or compromised FortiAP/FortiExtender/FortiSwitch endpoints. Monitor for malformed or anomalous CAPWAP traffic and unexpected CAPWAP daemon instability or crashes. Because available reporting indicates exploitation requires control of an authenticated or trusted endpoint, hardening management of downstream access devices and removing untrusted devices from the environment can reduce risk.

Remediation

Patch, then assume compromise.

Apply Fortinet's fixes for CVE-2025-53844 as provided in PSIRT advisory FG-IR-26-123 by upgrading affected FortiOS installations to a patched release. Affected branches identified in the provided content are 7.2, 7.4, and 7.6; specifically vulnerable versions include 7.6.0-7.6.3, 7.4.0-7.4.8, and 7.2.0-7.2.11. Use Fortinet's advisory as the authoritative source for exact fixed versions and upgrade targets.
PUBLIC EXPLOITS

Exploits

No public exploits tracked yet. Mallory keeps watching.

VALID 0 / 0 TOTALView more in app

No public exploit code observed for this vulnerability.

EXPOSURE SURFACE

Affected products & vendors

Products and vendors Mallory has correlated with this vulnerability. Open in Mallory to drill down to specific CPE configurations and version ranges.

VendorProductType
FortinetFortiosoperating_system

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What this page doesn’t show

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Threat actor evidence

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Associated malware

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Detection signatures

YARA, Sigma, Snort, and vendor rules, auto-deployed to your SIEM.

Vendor-by-vendor mapping

Cross-references every affected SKU, including bundled OEM variants.

Social activity2

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