CVE-2026-56104

Chainlit < 2.10.1 Session Hijacking via WebSocket Session Restoration

8.8 HighFix available

Chainlit before 2.10.1 contains a session hijacking vulnerability that allows unauthenticated attackers to restore and inherit authenticated user sessions by presenting a valid sessionId during WebSocket session restoration without ownership verification. Attackers can exploit the restore_existing_session path to assume a victim's permissions and roles, enabling unauthorized invocation of tools and access to data restricted to the authenticated victim.

Attack profile

How easy it is to exploit

Attack vector: Network
Complexity: High
Privileges needed: Low
User interaction: None

What an attacker can affect

Confidentiality: High
Integrity: High
Availability: None

Exploit likelihood

0.42%Up 0.1 points since Jun 23, 2026

What each source reports

CVE List Score used 8.8

Chainlit < 2.10.1 Session Hijacking via WebSocket Session Restoration

Record: CVE-2026-56104
CVSS 4.0: 8.8 HighCVSS:4.0/AV:N/AC:H/AT:N/PR:L/UI:N/VC:H/VI:H/VA:N/SC:H/SI:H/SA:N
CVSS 3.1: 8.2 HighCVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:N
Weakness: CWE-862
Updated: 2026-11-02

EUVDEUVD-2026-38285 8.8

Record: EUVD-2026-38285
CVSS 4.0: 8.8 HighCVSS:4.0/AV:N/AC:H/AT:N/PR:L/UI:N/VC:H/VI:H/VA:N/SC:H/SI:H/SA:N
Updated: 2026-11-02

GitHub AdvisoriesGHSA-c39v-8hrw-h448 9.1

Chainlit contains a session hijacking vulnerability

Record: GHSA-c39v-8hrw-h448
CVSS 4.0: 9.1 CriticalCVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N
CVSS 3.1: 7.4 HighCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N
Weakness: CWE-862
Updated: 2026-11-02

NVD 8.8

Record: CVE-2026-56104
CVSS 4.0: 8.8 HighCVSS:4.0/AV:N/AC:H/AT:N/PR:L/UI:N/VC:H/VI:H/VA:N/SC:H/SI:H/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: 8.2 HighCVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:N
Weakness: CWE-862
Updated: 2026-11-02

OSV 8.8

Chainlit < 2.10.1 Session Hijacking via WebSocket Session Restoration

Record: CVE-2026-56104
CVSS 4.0: 8.8 HighCVSS:4.0/AV:N/AC:H/AT:N/PR:L/UI:N/VC:H/VI:H/VA:N/SC:H/SI:H/SA:N
Weakness: CWE-862
Updated: 2026-11-02

OSVGHSA-c39v-8hrw-h448 9.1

Chainlit contains a session hijacking vulnerability

Record: GHSA-c39v-8hrw-h448
CVSS 4.0: 9.1 CriticalCVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N
CVSS 3.1: 7.4 HighCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N
Weakness: CWE-862
Updated: 2026-11-02

OSVPYSEC-2026-4028 9.1

Chainlit contains a session hijacking vulnerability

Record: PYSEC-2026-4028
CVSS 4.0: 9.1 CriticalCVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N
CVSS 3.1: 7.4 HighCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N
Updated: 2026-11-02

Affected products

chainlit

Affected packages

Affected packages
Package	Affected	Fixed
`chainlit` PyPI	before 2.10.1	2.10.1
`chainlit` PyPI	before 2.10.1, plus listed versions 0.1.00.1.10.1.1010.1.1020.1.103 Show 45 moreShow less 0.2.00.2.10.2.1010.2.1020.2.1030.2.1040.2.1050.2.1060.2.1070.2.1080.2.1090.2.1100.2.1110.3.00.4.00.4.10.4.1010.4.20.4.30.5.00.5.10.5.20.6.00.6.10.6.20.6.30.6.40.6.4010.6.4020.7.00.7.10.7.20.7.30.7.3010.7.4000.7.5000.7.5010.7.600rc00.7.600rc10.7.601rc00.7.6020.7.602rc00.7.6030.7.6040.7.604rc0	2.10.1

History

History
Recorded	Changed	Sources
Nov 2, 2026	first indexed	CVE List, EUVD, GitHub Advisories, NVD, OSV

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

In short

CVE-2026-56104 is a high vulnerability (CVSS 8.8) in Chainlit, published June 22, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.42%, the 36th percentile. Fixed in chainlit 2.10.1.

References

This page doesn't list everything

Left out here: 115 versions. The JSON record has them.