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CVE-2026-59804

Midscene Bridge Server - Session Hijack via Unauthenticated WebSocket

7.6 High

Midscene Bridge Server through 1.10.3, fixed in commit 86f4118, contains a missing authentication and CORS misconfiguration vulnerability that allows unauthenticated remote attackers to hijack active bridge sessions by opening a cross-origin WebSocket connection to the local Socket.IO server, which performs no Origin header validation and requires no authentication token. Attackers can connect from any web page visited by the victim to seize the single-client slot, intercept and inject automation commands, exfiltrate command-payload data, or unconditionally terminate the server by supplying the MIDSCENE_BRIDGE_SIGNAL_KILL query parameter.

Attack profile

How easy it is to exploit

Attack vector
Network
Complexity
High
Privileges needed
None
User interaction
Passive

What an attacker can affect

Confidentiality
High
Integrity
High
Availability
None

Exploit likelihood

0.31%Up 0.1 points since Jul 9, 2026
90%50%10%1%

What each source reports

CVE List Score used 7.6

Midscene Bridge Server - Session Hijack via Unauthenticated WebSocket

Midscene Bridge Server through 1.10.3, fixed in commit 86f4118, contains a missing authentication and CORS misconfiguration vulnerability that allows unauthenticated remote attackers to hijack active bridge sessions by opening a cross-origin WebSocket connection to the local Socket.IO server, which performs no Origin header validation and requires no authentication token. Attackers can connect from any web page visited by the victim to seize the single-client slot, intercept and inject automation commands, exfiltrate command-payload data, or unconditionally terminate the server by supplying the MIDSCENE_BRIDGE_SIGNAL_KILL query parameter.

Record
CVE-2026-59804
CVSS 4.0
7.6 HighCVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:P/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N
CVSS 3.1
6.8 MediumCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:N
Weakness
CWE-1385, CWE-306
Updated
2026-11-02
EUVDEUVD-2026-42373 7.6

Midscene Bridge Server through 1.10.3, fixed in commit 86f4118, contains a missing authentication and CORS misconfiguration vulnerability that allows unauthenticated remote attackers to hijack active bridge sessions by opening a cross-origin WebSocket connection to the local Socket.IO server, which performs no Origin header validation and requires no authentication token. Attackers can connect from any web page visited by the victim to seize the single-client slot, intercept and inject automation commands, exfiltrate command-payload data, or unconditionally terminate the server by supplying the MIDSCENE_BRIDGE_SIGNAL_KILL query parameter.

Record
EUVD-2026-42373
CVSS 4.0
7.6 HighCVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:P/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N
Updated
2026-11-02
GitHub AdvisoriesGHSA-8rcx-4rjr-4wpf 7.6

Midscene Bridge Server through 1.10.3, fixed in commit 86f4118, contains a missing authentication...

Midscene Bridge Server through 1.10.3, fixed in commit 86f4118, contains a missing authentication and CORS misconfiguration vulnerability that allows unauthenticated remote attackers to hijack active bridge sessions by opening a cross-origin WebSocket connection to the local Socket.IO server, which performs no Origin header validation and requires no authentication token. Attackers can connect from any web page visited by the victim to seize the single-client slot, intercept and inject automation commands, exfiltrate command-payload data, or unconditionally terminate the server by supplying the MIDSCENE_BRIDGE_SIGNAL_KILL query parameter.

Record
GHSA-8rcx-4rjr-4wpf
CVSS 4.0
7.6 HighCVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:P/VC:H/VI:H/VA:N/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
CVSS 3.1
6.8 MediumCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:N
Weakness
CWE-306
Updated
2026-11-02
NVD 7.6

Midscene Bridge Server through 1.10.3, fixed in commit 86f4118, contains a missing authentication and CORS misconfiguration vulnerability that allows unauthenticated remote attackers to hijack active bridge sessions by opening a cross-origin WebSocket connection to the local Socket.IO server, which performs no Origin header validation and requires no authentication token. Attackers can connect from any web page visited by the victim to seize the single-client slot, intercept and inject automation commands, exfiltrate command-payload data, or unconditionally terminate the server by supplying the MIDSCENE_BRIDGE_SIGNAL_KILL query parameter.

Record
CVE-2026-59804
CVSS 4.0
7.6 HighCVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:P/VC:H/VI:H/VA:N/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
CVSS 3.1
6.8 MediumCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:N
Weakness
CWE-306, CWE-1385
Updated
2026-11-02
OSV 7.6

Midscene Bridge Server - Session Hijack via Unauthenticated WebSocket

Midscene Bridge Server through 1.10.3, fixed in commit 86f4118, contains a missing authentication and CORS misconfiguration vulnerability that allows unauthenticated remote attackers to hijack active bridge sessions by opening a cross-origin WebSocket connection to the local Socket.IO server, which performs no Origin header validation and requires no authentication token. Attackers can connect from any web page visited by the victim to seize the single-client slot, intercept and inject automation commands, exfiltrate command-payload data, or unconditionally terminate the server by supplying the MIDSCENE_BRIDGE_SIGNAL_KILL query parameter.

Record
CVE-2026-59804
CVSS 4.0
7.6 HighCVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:P/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N
Weakness
CWE-1385, CWE-306
Updated
2026-11-02

Affected products

History

History
RecordedChangedSources
first indexedCVE List, EUVD, GitHub Advisories, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2026-59804 is a high vulnerability (CVSS 7.6) in Web-infra-dev Midscene, published July 8, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.31%, the 23rd percentile. No source names a fixed version.

References

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