CVE-2026-82259
SvelteKit 2.49.0 before 2.53.3 Denial of Service via form
SvelteKit versions from 2.49.0 through 2.53.2 (fixed in 2.53.3) contain a deserialization expansion issue in the experimental form remote function. When an application enables experimental.remoteFunctions and uses the form function to process the files array without validating files.length or individual file sizes, an attacker can submit relatively small inputs that expand into very large file arrays, leading to expensive processing and denial of service.
Attack profile
How easy it is to exploit
- Attack vector
- Network
- Complexity
- Low
- Privileges needed
- None
- User interaction
- None
What an attacker can affect
- Confidentiality
- None
- Integrity
- None
- Availability
- High
Exploit likelihood
What each source reports
CVE List Score used
8.7
SvelteKit 2.49.0 before 2.53.3 Denial of Service via form
SvelteKit versions from 2.49.0 through 2.53.2 (fixed in 2.53.3) contain a deserialization expansion issue in the experimental form remote function. When an application enables experimental.remoteFunctions and uses the form function to process the files array without validating files.length or individual file sizes, an attacker can submit relatively small inputs that expand into very large file arrays, leading to expensive processing and denial of service.
- Record
CVE-2026-82259- CVSS 4.0
- 8.7 High
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N - CVSS 3.1
- 7.5 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H - Weakness
- CWE-502
- Updated
- 2026-11-02
EUVDEUVD-2026-67585
8.7
SvelteKit versions from 2.49.0 through 2.53.2 (fixed in 2.53.3) contain a deserialization expansion issue in the experimental form remote function. When an application enables experimental.remoteFunctions and uses the form function to process the files array without validating files.length or individual file sizes, an attacker can submit relatively small inputs that expand into very large file arrays, leading to expensive processing and denial of service.
- Record
EUVD-2026-67585- CVSS 4.0
- 8.7 High
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N - Updated
- 2026-11-02
GitHub AdvisoriesGHSA-7jhg-723h-fjhx
8.7
SvelteKit versions from 2.49.0 through 2.53.2 (fixed in 2.53.3) contain a deserialization...
SvelteKit versions from 2.49.0 through 2.53.2 (fixed in 2.53.3) contain a deserialization expansion issue in the experimental form remote function. When an application enables experimental.remoteFunctions and uses the form function to process the files array without validating files.length or individual file sizes, an attacker can submit relatively small inputs that expand into very large file arrays, leading to expensive processing and denial of service.
- Record
GHSA-7jhg-723h-fjhx- CVSS 4.0
- 8.7 High
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/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
- 7.5 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H - Weakness
- CWE-502
- Updated
- 2026-11-02
GitHub AdvisoriesGHSA-fpg4-jhqr-589c
1.7
SvelteKit has deserialization expansion in unvalidated `form` remote function leading to Denial of Service (experimental only)
Some relatively small inputs can cause very large files arrays in form handlers. If the SvelteKit application code doesn't check files.length or individual files' sizes and performs expensive processing with them, it can result in Denial of Service.
Only users with experimental.remoteFunctions: true who are using the form function and are processing the files array without validation are vulnerable.
- Record
GHSA-fpg4-jhqr-589c- CVSS 4.0
- 1.7 Low
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:U - Weakness
- CWE-770
- Updated
- 2026-11-02
NVD
8.7
SvelteKit versions from 2.49.0 through 2.53.2 (fixed in 2.53.3) contain a deserialization expansion issue in the experimental form remote function. When an application enables experimental.remoteFunctions and uses the form function to process the files array without validating files.length or individual file sizes, an attacker can submit relatively small inputs that expand into very large file arrays, leading to expensive processing and denial of service.
- Record
CVE-2026-82259- CVSS 4.0
- 8.7 High
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/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
- 7.5 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H - Weakness
- CWE-502
- Updated
- 2026-11-02
OSV
8.7
SvelteKit 2.49.0 before 2.53.3 Denial of Service via form
SvelteKit versions from 2.49.0 through 2.53.2 (fixed in 2.53.3) contain a deserialization expansion issue in the experimental form remote function. When an application enables experimental.remoteFunctions and uses the form function to process the files array without validating files.length or individual file sizes, an attacker can submit relatively small inputs that expand into very large file arrays, leading to expensive processing and denial of service.
- Record
CVE-2026-82259- CVSS 4.0
- 8.7 High
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N - Weakness
- CWE-502
- Updated
- 2026-11-02
OSVGHSA-fpg4-jhqr-589c
1.7
SvelteKit has deserialization expansion in unvalidated `form` remote function leading to Denial of Service (experimental only)
Some relatively small inputs can cause very large files arrays in form handlers. If the SvelteKit application code doesn't check files.length or individual files' sizes and performs expensive processing with them, it can result in Denial of Service.
Only users with experimental.remoteFunctions: true who are using the form function and are processing the files array without validation are vulnerable.
- Record
GHSA-fpg4-jhqr-589c- CVSS 4.0
- 1.7 Low
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:U - Weakness
- CWE-770
- Updated
- 2026-11-02
Affected products
Affected packages
| Package | Affected | Fixed |
|---|---|---|
@sveltejs/kitnpm |
2.49.0 to 2.53.2 | 2.53.3 |
@sveltejs/kitnpm |
2.49.0 up to 2.53.3 | 2.53.3 |
History
| Recorded | Changed | Sources |
|---|---|---|
| first indexed | CVE List, EUVD, GitHub Advisories, NVD, OSV |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2026-82259 is a high vulnerability (CVSS 8.7) in Svelte Sveltekit, published February 28, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.53%, the 45th percentile. Fixed in @sveltejs/kit 2.53.3.
References
github.com/sveltejs/kit/security/advisories/GHSA-fpg4-jhqr-589c
vulncheck.com/advisories/sveltekit-2.49.0-before-2.53.3-denial-of-service-via-form
nvd.nist.gov/vuln/detail/CVE-2026-82259
github.com/advisories/GHSA-7jhg-723h-fjhx
github.com/sveltejs/kit/commit/faba869db3644077169bf5d7c6e41fd5f3d6c65e
github.com/sveltejs/kit/releases/tag/@sveltejs/[email protected]
github.com/advisories/GHSA-fpg4-jhqr-589c
github.com/CVEProject/cvelistV5/tree/main/cves/2026/82xxx/CVE-2026-82259.json
github.com/sveltejs/kit