Rejetto HFS CVE-2026-61500
CRITICALSeverity by source
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
Network, unauthenticated (PR:N/UI:N) path to admin RCE gives C/I/A High; AC:H reflects the sampling and PRNG-state reconstruction needed to recover the key.
Primary rating from Vendor (VulnCheck).
CVSS VectorVendor: VulnCheck
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
Lifecycle Timeline
3DescriptionCVE.org
Rejetto HFS 3.0.0 through 3.2.0 derives its session-cookie signing key from the non-cryptographic Math.random() generator and discloses outputs of the same generator to unauthenticated clients during login. A remote attacker can collect a small number of login responses, reconstruct the generator's state, recover the signing key, and forge a valid administrator session cookie, leading to full administrative access and remote code execution via the server_code configuration feature.
AnalysisAI
Administrator session forgery in Rejetto HFS (HTTP File Server) versions 3.0.0 through 3.2.0 lets a remote unauthenticated attacker derive the server's session-cookie signing key. Because HFS seeds that key from JavaScript's non-cryptographic Math.random() and simultaneously leaks outputs of the same generator to clients during login, an attacker can sample a few login responses, reconstruct the PRNG state, and mint a valid admin cookie - yielding full administrative control and remote code execution through the server_code configuration feature. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | Exploitation requires that the HFS instance (versions 3.0.0-3.2.0) be network-reachable and that its login endpoint be accessible to the attacker, because the attack depends on collecting the Math.random() outputs disclosed in login responses to reconstruct the signing key. … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | The vendor CVSS 4.0 vector (AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H, score 9.3) rates this critical with no authentication and full confidentiality/integrity/availability impact, consistent with unauthenticated forgery leading to RCE. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | An attacker who can reach an internet-exposed HFS 3.x login page sends a small number of unauthenticated login requests and records the Math.random()-derived values leaked in the responses. Using those samples they reconstruct the generator's internal state offline, regenerate the session-cookie signing key, and forge a signed administrator cookie; presenting that cookie grants full admin access, after which they use the server_code configuration feature to execute arbitrary commands on the host. … |
| Remediation | Vendor-released patch: 3.2.1 - upgrade every HFS instance to v3.2.1 or later immediately, as it addresses multiple session/authentication weaknesses affecting all prior 3.x versions (https://github.com/rejetto/hfs/releases/tag/v3.2.0...v3.2.1 changelog; release: https://github.com/rejetto/hfs/releases/tag/v3.2.1). … Detailed patch versions, workarounds, and compensating controls in full report. |
Recommended ActionAI
Within 24 hours, identify all Rejetto HFS instances on your network and determine which are running versions 3.0.0-3.2.0; immediately isolate or disable external network access to affected servers. …
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Path traversal via the `lang` query parameter in Rejetto HFS 3.0.0 through 3.2.0 enables remote unauthenticated attacker
Username enumeration in Rejetto HFS 3.0.0-3.2.0 exposes valid account names-including the default admin account-to remot
Stored cross-site scripting in Rejetto HTTP File Server 3.0.0-3.2.0 allows an unauthenticated remote attacker to inject
Rejetto HTTP File Server (HFS) versions 3.0.0 through 3.2.0 performs state-changing administrative operations via HTTP G
Stored XSS in Rejetto HFS 3.0.0 through 3.2.0 allows attackers with upload access - or any user on servers configured wi
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External POC / Exploit Code
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