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Fencer Intel
low 2.3

CVE-2025-40710 json

Host Header Injection (HHI) in the Hotspot Shield VPN client

published last yr. modified 4mo ago also EUVD-2025-19527

cvss
2.3
version 4.0, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.3%
EPSS 0.3% chance of exploitation in 30 days, percentile 24%
public exploits
0
none known

Summary

Host Header Injection (HHI) vulnerability in the Hotspot Shield VPN client, which can induce unexpected behaviour when accessing third-party web applications through the VPN tunnel. Although such applications do not present this vulnerability per se, the use of the tunnel, together with a forged Host header, can cause the VPN client to redirect or forward HTTP requests to servers other than those originally intended, leading to consequences such as open redirects or delivery of traffic to infrastructure controlled by an attacker. This does not imply a flaw in the target applications, but in how the VPN client internally handles outgoing headers and requests.

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CISA SSVC

Exploitation
none
Automatable
no
Technical impact
partial
Assessed
last yr.

Exploit prediction

0.32% chance of exploitation in the next 30 days, higher than 24% of all scored CVEs (FIRST EPSS, 2026-11-09).

CVSS scores

assigned by version score vector
CNA 4.0 2.3 CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:P/VC:N/VI:N/VA:L/SC:N/SI:L/SA:N
CNA 4.0 2.3 CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:P/VC:N/VI:N/VA:L/SC:N/SI:L/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

Affected products

  • Hotspot Shield Hotspot Shield VPN client

Classification

Weakness
  • CWE-74 Improper Neutralization of Special Elements in Output Used by a Downstream Component

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.