CVE-2026-40074
Svelte Kit ≤ 2.57.1
Raw vector
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:L/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:XSummary
CVE-2026-40074 is a medium-severity Improper Handling of Exceptional Conditions (CWE-755) vulnerability in Svelte Kit. Its CVSS base score is 6.3 (Medium).
Operationally, exploitation aligns with the MITRE ATT&CK technique Exploitation for Client Execution (T1203); ranked at the 29th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.
The strongest mitigations our analysis identified map to SC-24 (Fail in Known State) and SI-17 (Fail-safe Procedures) — see the control section below for these in your framework.
Deeper analysis AI-assisted summary
Synthesised by an AI model from the NVD description and linked references — a reading aid, not an authoritative source.
CVE-2026-40074 affects SvelteKit, a framework for building robust web applications with Svelte, in versions prior to 2.57.1. The vulnerability arises when the redirect function is invoked from within the handle server hook using a location parameter that includes characters invalid for HTTP headers. This triggers an unhandled TypeError, which can disrupt application availability. The issue is classified under CWE-755 (Improper Handling of Exceptional Conditions) with a CVSS v3.1 base score of 7.5 (AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H), indicating high-impact availability disruption without requiring authentication or user interaction.
Attackers can exploit this remotely over the network with low complexity by supplying malicious input to the location parameter, particularly if applications pass unsanitized user data to the redirect function in the handle server hook. Successful exploitation results in a denial-of-service condition on affected platforms, crashing the server process and potentially halting service until restart. No privileges or user interaction are needed, making it accessible to unauthenticated remote actors.
The SvelteKit security advisory (GHSA-3f6h-2hrp-w5wx) and release notes for version 2.57.1 detail the fix, implemented via commit 10d7b44425c3d9da642eecce373d0c6ef83b4fcd. Security practitioners should upgrade to SvelteKit 2.57.1 or later to mitigate the issue, and review applications for unsanitized user input in redirect locations within handle hooks.
OWASP Top 10 for Web (2025)
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-21504
Vulnerability Data
SvelteKit is a framework for rapidly developing robust, performant web applications using Svelte. Prior to 2.57.1, redirect, when called from inside the handle server hook with a location parameter containing characters that are invalid in a HTTP header, will cause…
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an unhandled TypeError. This could result in DoS on some platforms, especially if the location passed to redirect contains unsanitized user input. This vulnerability is fixed in 2.57.1.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise Techniques
CVEs Like This One
Affected Assets
Mitigating Controls
Control response
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- 1 hardening rule · 1 OS baseline
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Mitigating Controls (NIST 800-53 r5) AI
Requires the system to fail to a known safe state on specified failures, limiting the impact of unhandled exceptional conditions.
Mandates explicit fail-safe procedures triggered by indicated failures, structurally preventing unhandled or mishandled exceptional conditions.
Requires generation of appropriate error messages on exceptional conditions, directly enforcing correct handling rather than silent or incorrect behavior.
Mitigating Controls (NIST CSF 2.0) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.
Secure SDLC practices explicitly require proper exception and error handling during design and coding.
Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.
Security testing in development and acceptance verifies correct handling of exceptional conditions.
Documented operating procedures may specify exception handling but do not guarantee implementation.
Logging captures unhandled exceptions, aiding detection but not preventing the weakness.
Monitoring can surface unhandled exceptions but does not enforce proper handling.
Secure SDLC mandates exception-handling requirements and testing that directly prevent improper handling of exceptional conditions.
Application security requirements explicitly include handling of error and exceptional conditions.