Authentication Bypass and Privilege Escalation in Fortinet FortiSandbox JRPC API
CVE-2026-39813 is a critical path traversal vulnerability in the Fortinet FortiSandbox JRPC API. The flaw is described as a '../filedir' path traversal issue affecting FortiSandbox 4.4.0 through 4.4.8 and 5.0.0 through 5.0.5. Based on the provided content, a remote, unauthenticated attacker can send specially crafted HTTP requests to the JRPC API to bypass authentication controls. Fortinet and supporting reporting characterize the issue as an API privilege escalation vulnerability caused by path traversal, with successful exploitation allowing escalation of privilege on the affected system.
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Impact, mitigation & remediation
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Impact
What an attacker gets, and what they’ve been doing with it.
Mitigation
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Remediation
Patch, then assume compromise.
Exploits
1 valid exploit after Mallory filtered fakes, detection scripts, and README-only repos (1 hidden).
This repository is a small exploit repo with 3 files: a Python PoC, a Nuclei template, and a README. Because it includes a Nuclei template, it is part of a framework; the main exploit logic is captured in CVE-2026-39808.yaml, while the Python script provides a standalone implementation of the same attack chain. The exploit targets Fortinet FortiSandbox and chains an unauthenticated access check against /api/v1/system/firmware (described as CVE-2026-39813 auth bypass) with a command injection in /fortisandbox/job-detail/tracer-behavior via the jid parameter (CVE-2026-39808). The injected command writes output to /web/ng/out.txt, which is then retrieved from /ng/out.txt to confirm root-level execution. The Nuclei template fingerprints the login page, extracts version information, triggers a benign id payload, and verifies success by matching uid=0/gid=0 in the output. Overall, this is a real unauthenticated web RCE PoC for vulnerable FortiSandbox versions, providing root command execution and simple output exfiltration through a web-accessible file.
Affected products & vendors
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Recent activity
38 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.
A critical path traversal vulnerability in the FortiSandbox JRPC API that may allow unauthenticated attackers to bypass authentication using crafted HTTP requests.
A critical Fortinet FortiSandbox vulnerability that allows unauthenticated attackers to escalate privileges and execute unauthorized code remotely via low-complexity command injection without user interaction.
Unknown
A path traversal vulnerability in FortiSandbox's JRPC API that could allow unauthenticated attackers to bypass authentication.
The version that knows your environment.
Query your assets running an affected version, and investigate the blast radius.
Every observed campaign linking this CVE to a named adversary.
Malware families riding this exploit, with evidence and IOCs.
YARA, Sigma, Snort, and vendor rules, auto-deployed to your SIEM.
Cross-references every affected SKU, including bundled OEM variants.
Community discussion across Reddit, Mastodon, and other social sources.