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CVE-2026-42239 Budibase CVE debrief

CVE-2026-42239 is a high-severity vulnerability in Budibase, an open-source low-code platform. The issue arises from the insecure setting of the `budibase:auth` cookie, which contains the JWT session token. Specifically, the cookie is set with `httpOnly: false`, allowing JavaScript to access it via `document.cookie`. This makes every cross-site scripting (XSS) vulnerability a full account takeover, as an attacker can steal the JWT and gain persistent access to the victim's account. Additionally, the cookie lacks the `secure: true` attribute, meaning it is sent over plaintext HTTP, and the `sameSite` attribute, further increasing the risk. This vulnerability has been patched in version 3.35.10 of Budibase.

Vendor
Budibase
Product
Unknown
CVSS
HIGH 8.1
CISA KEV
Not listed in stored evidence
Original CVE published
2026-05-07
Original CVE updated
2026-06-04
Advisory published
2026-05-07
Advisory updated
2026-06-04

Who should care

Developers and administrators using Budibase versions prior to 3.35.10 should be aware of this vulnerability and take immediate action to update their installations. Security teams monitoring for XSS vulnerabilities in low-code platforms should also be aware of this issue.

Technical summary

The `budibase:auth` cookie is set with insecure attributes, specifically `httpOnly: false`, allowing JavaScript access via `document.cookie`. The cookie also lacks `secure: true` and `sameSite` attributes. This vulnerability enables full account takeover via XSS attacks.

Defensive priority

High

Recommended defensive actions

  • Update Budibase to version 3.35.10 or later.
  • Review and adjust cookie settings for secure attributes.
  • Implement additional security measures to prevent XSS attacks.

Evidence notes

CVE-2026-42239 has a CVSS score of 8.1 and is classified as HIGH severity. The vulnerability was published on 2026-05-07 and modified on 2026-06-04.

Sources and references

Verified primary and authoritative sources

  • CVE-2026-42239 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-42239

    CVE Program - Official CVE Program record with source-provided CVE metadata.

  • CVE-2026-42239 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-42239

    NIST National Vulnerability Database - Official NIST NVD detail page and source-specific vulnerability assessment.

Supplemental references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.