CVE
kit denial of service in remote form function parsing
Only affects @sveltejs/kit 2.42.0 through 3.1.0 applications using the experimental remote functions flag with form, query, or command remote functions. Fixed in 3.1.1.
Written by anthropic/claude-haiku-5.5 from the sources below. Verify against them.
- Exploited
- No known exploitation
- Fix
- Fixed in 3.1.1
- Who is exposed
- Specific setups only
Do first: Check whether your setup matches what the bug needs. Applications using the experimental remote functions flag Applications using a remote form, query or command function @sveltejs/kit versions from 2.42.0 through 3.1.0
- Published
- Last modified
- Whether it needs action now or is a reference record, by fixed rules, with why. Last checked is when cve.now last re-read it.What do these mean? →
- Reference
- Last checked
- A 0-100 score for how much a CVE matters across the industry: exploitation, exposure, how widely the software is used, severity and whether a fix exists.What do these mean? →
- 20/100 · provisional
- How many real-world setups can hit the bug, from the vendor's advisory and CISA data. It does not know your setup.What do these mean? →
- Specific setups only
- Whether working attack code is public (Exploit-DB, Metasploit, Nuclei or GitHub). Public code makes attacks easier.What do these mean? →
- None on Exploit-DB, Metasploit or GitHub
Summary
SvelteKit, the web application framework, is affected when it uses the experimental remote functions feature with a remote form function. An attacker can send a specially crafted request with many form entries over the network, without logging in, to make the server block for an extended period and deny service.
Read the original description
SvelteKit is a framework for rapidly developing robust, performant web applications using Svelte. From version 2.42.0 until 3.1.1, applications using the experimental remote functions flag and a remote form function could perform quadratic synchronous work while parsing a specially crafted request with many form entries. The parsing work could block the event loop for an extended period and deny service. This issue is fixed in 3.1.1.
Who should check
Teams running SvelteKit 2.42.0 through 3.1.0 with the experimental remote functions flag and remote form, query or command functions.
Read the source excerpt
“This only affects applications using the experimental remote functions flag”
cve.now Index
- Exploitation?/40Unknown. No CISA SSVC exploitation rating yet
- Exposure12/25Specific setups only, reachable over the network without a login
- Reach?/20Unknown. No tracked technology or package matched
- Severity7.5/10CVSS 7.5
- No patch0/5No signal
What would change the score
- Would score about 70 if added to CISA KEV
- Would score about 65 if CISA's SSVC rates exploitation active
What to do
Check whether your setup matches what the bug needs.
Applications using the experimental remote functions flag Applications using a remote form, query or command function @sveltejs/kit versions from 2.42.0 through 3.1.0Upgrade to a fixed version: 3.1.1.
Check your systems with an agent
Paste this into a coding or ops agent. It checks your systems read-only and reports a table per asset.
Check whether my systems are affected by CVE-2026-128120 (SvelteKit: DoS while parsing form data from a remote functions `form`), using the cve.now data below.
Rules: work read-only. Do not run exploit code, proof-of-concept scripts or scanners that send attack payloads, and do not change any configuration, package, image or deployment. Report findings only.
What cve.now has for CVE-2026-128120 (entry last updated 2026-11-13):
Affected:
- sveltejs kit: from 2.42.0, fixed in 3.1.1
Fixed versions: 3.1.1.
Conditions (all must be true for the bug to be hit):
- Applications using the experimental remote functions flag (source: https://github.com/sveltejs/kit/security/advisories/GHSA-3r8g-jcqq-3p5j)
- Applications using a remote form, query or command function (source: https://github.com/sveltejs/kit/security/advisories/GHSA-3r8g-jcqq-3p5j)
- @sveltejs/kit versions from 2.42.0 through 3.1.0 (source: https://github.com/sveltejs/kit/security/advisories/GHSA-3r8g-jcqq-3p5j)
Setup: the bug needs a feature or setting that is off by default or uncommon. Check whether each asset has it on.
Attacker needs: network access, no login, no user action.
CISA KEV: CVE-2026-128120 is not listed as of cve.now's last read.
This KEV status is for CVE-2026-128120 only. If you also check another CVE, look up its own KEV status; never assume it from this one.
How to check:
- Installed software: check what is actually running, not what a repo declares. Read the version from each host, container image and Kubernetes node (the binary's version output, the OS package database, image layers), and check whether the conditions above hold there. Distribution packages may carry a backported fix under an older version number; confirm against the distribution's own advisory.
Verify against the linked advisories before concluding, and cite the date you read each one:
- https://github.com/sveltejs/kit/security/advisories/GHSA-3r8g-jcqq-3p5j
- https://github.com/sveltejs/kit/commit/24d8ee409d83c438330ff2850b4f159c1222aa27
- https://github.com/sveltejs/kit/releases/tag/@sveltejs/kit@3.1.1
Do not conclude an asset is unaffected unless you checked it and the evidence covers both its version and the conditions above. If you could not check something, mark it unknown and say what is missing.
Report a table with one row per asset and these columns: Asset | Version or build | Status (affected, fixed, not applicable, unknown) | Compensating controls | Exposure (internet-facing, internal, none) | Evidence | Next action.
Entry: https://cve.now/CVE-2026-128120
For follow-up questions, use the cve.now MCP server at https://mcp.cve.now/mcp (no authentication), for example execute with name cve.get and arguments {"id": "CVE-2026-128120"}.Timeline
- CVE published
- First seen by cve.now
Affected versions
- sveltejs kit
From 2.42.0 · fixed in 3.1.1
Evidence 4
Vendor advisory · 1
Establishes: Affected and fixed versions.
- Advisory
Other links · 2
- Repository
- Repository
Corrections
None so far.
Something wrong on this page? Report an error. Every fix is listed here.
Questions about CVE-2026-128120
Is CVE-2026-128120 being exploited?
It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked.Source: cve.now feed data
What does this mean?
A specially-crafted request can block the server's event loop for extended periods while form data is parsed, which causes a denial of service.Source: github.com
Which versions are affected by CVE-2026-128120?
kit: from 2.42.0 before 3.1.1.Source: cve.now feed data
Am I affected, and how do I check?
@sveltejs/kit versions 2.42.0 through 3.1.0 are in the affected range, and only applications that use the experimental remote functions flag with form, query, or command remote functions are covered. To check, run npm ls @sveltejs/kit to see the installed version, and look in the app's configuration for whether the experimental remote functions flag is enabled.Source: github.com
How do I fix CVE-2026-128120?
Upgrade @sveltejs/kit to 3.1.1 or later, which is the fixed version listed for this range.Source: github.com