Critical severity · published Jul 13, 2026
CVE-2026-61500
Rejetto HFS < 3.2.1 Session Forgery via Predictable Signing Key
9.8
CVSS
1.9%
EPSS
No
On KEV
Description
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.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
High
Integrity
High
Availability
High
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)1.9% · higher than 80% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
HF
hfs · rejetto
3.0.0 before 3.2.1 · source: vendor
In the news
VulnerabilityCritical
Rejetto HFS servers now actively scanned for critical RCE flaw
Hackers are actively scanning for a Rejetto HFS weak signing key vulnerability, tracked as CVE-2026-61500, that allows session forgery, account takeover, and remote code execution (RCE). [...]
Oct 5, 2026·BleepingComputer
VulnerabilityCritical
Attackers Target Rejetto HFS Flaw That Enables Admin Session Forgery and RCE
A critical security flaw impacting Rejetto HTTP File Server (HFS) is witnessing active exploitation attempts, according to VulnCheck.
The vulnerability in question is CVE-2026-61500 (CVSS score: 9.3), a case of session forgery stemming from the use of a weak pseudo-random number generator (PRNG) that can lead to a predictable key, which an attacker can then use to gain unauthorized access and
Oct 5, 2026·The Hacker News
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-61500
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-61500
release-notes
https://github.com/rejetto/hfs/releases/tag/v3.2.1
third-party-advisory
https://www.vulncheck.com/advisories/rejetto-hfs-session-forgery-via-predictable-signing-key
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