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VulnerabilityPublished

CVE-2026-128123: sveltejs kit · Uncaught Exception

Affects sveltejs kitSource CVE Database V5

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Not known to be exploited · CVSS 5.9 Medium : upgrade to 3.1.1 or 2.70.4 when convenient.

Data as of 13 Nov 2026, 20:05 UTC

CVSS 3.1 base score
5.9Medium
How severe the flaw is on the 0–10 CVSS scale.

Thin evidence

One scorer or none
CVSS scores by source
CNA (GitHub_M)CVSS 3.15.9
Patch
Available – fixed in 3.1.1, 2.70.4, 6.0.1 +1
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 13 Nov 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 13 Nov 2026.

What to do

Upgrade kit to 3.1.1 or 2.70.4; adapter-node to 6.0.1 or 5.5.8.

Affected software

ProductAffectedFixed in
sveltejskitAffected
  • >=3.0.0-next.0 <3.1.1
Fixed in
  • 3.1.1
sveltejskitAffected
  • <2.70.4
Fixed in
  • 2.70.4
@sveltejsadapter-nodeAffected
  • >=6.0.0-next.0 <6.0.1
Fixed in
  • 6.0.1
@sveltejsadapter-nodeAffected
  • >=5.5.7 <5.5.8
Fixed in
  • 5.5.8

AI-suggested

This vulnerability is fixed in SvelteKit versions 5.5.8, 6.0.1, 3.1.1, and 2.70.4. Users should upgrade to these versions or later to remediate the issue. No additional mitigation is required once the upgrade is applied.

Description

CVE-2026-128123 is a vulnerability in SvelteKit framework versions 5.5.7 up to but not including 5.5.8 and 6.0.0-next.0 up to but not including 6.0.1, as well as versions >=3.0.0-next.0 <3.1.1 and <2.70.4. The issue occurs in the @sveltejs/adapter-node where an attempt to add a header to an immutable request causes the server to crash, resulting in a denial of service. This flaw is fixed in versions 5.5.8, 6.0.1, 3.1.1, and 2.70.4. The CVSS score is 5.9, indicating a medium severity impact primarily due to availability disruption.

References

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