EUVD-2026-38285
GHSA-c39v-8hrw-h448
Severity by source
CVSS: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
Network-reachable WebSocket, no attacker auth (PR:N) but requires obtaining a valid sessionId (AC:H); scope changes as attacker gains victim's identity/permissions; no availability impact.
Primary rating from Vendor (VulnCheck).
CVSS VectorVendor: VulnCheck
CVSS: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
Lifecycle Timeline
7DescriptionCVE.org
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.
AnalysisAI
Session hijacking in Chainlit before 2.10.1 allows remote attackers with a valid victim sessionId to inherit an authenticated user's session via the WebSocket restore_existing_session path, which fails to verify session ownership. Successful exploitation grants the attacker the victim's roles and permissions, enabling unauthorized tool invocation and access to restricted data. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | Attacker must possess a valid, currently-active sessionId belonging to an authenticated Chainlit user and must be able to reach the Chainlit WebSocket endpoint over the network. … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | The CVSS 4.0 base score of 8.8 reflects network reach with high confidentiality and integrity impact on both the vulnerable and a subsequent system (the connected backend tools and data), but AC:H and PR:L indicate exploitation is non-trivial and requires the attacker to first obtain a valid victim sessionId - for example via log leakage, referrer exposure, XSS, or network interception. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | An attacker who obtains a valid Chainlit sessionId for an authenticated user - for example from a leaked browser log, a shared screenshot, an HTTP referrer, or a network capture - opens a WebSocket connection and invokes the restore_existing_session path with that sessionId. Chainlit rebinds the existing authenticated identity to the attacker's socket, allowing them to invoke tools and read data as the victim. … |
| Remediation | Vendor-released patch: upgrade Chainlit to 2.10.1 or later (https://github.com/Chainlit/chainlit/releases/tag/2.10.1), which adds session-ownership validation on WebSocket restore via PR #2857 (commit 5effb664f1e0af4a4f0a42fe63ea979676039a7f). … Detailed patch versions, workarounds, and compensating controls in full report. |
Recommended ActionAI
24 hours: Inventory all Chainlit deployments, identify current versions, and determine criticality of systems running vulnerable versions. …
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Arbitrary file read in Chainlit versions prior to 2.9.4 lets an authenticated user disclose any file readable by the Cha
Same weakness CWE-862 – Missing Authorization
View allSame technique Authentication Bypass
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External POC / Exploit Code
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