# Payload authentication token field handling issue Advisory record · `GHSA-66wr-7vmr-p5jq` - **Identifiers:** `GHSA-66wr-7vmr-p5jq` · `CVE-2026-105863` - **State:** Confirmed - **Severity:** CVSS 9.2 Critical - **Critical:** Yes: CVSS 9+ - **Weakness (CWE):** [CWE-290](https://cwe.mitre.org/data/definitions/290.html) · [CWE-915](https://cwe.mitre.org/data/definitions/915.html) - **Tags:** [Authentication bypass](https://agentprime.io/advisories/tag/auth-bypass.md) · [Broken access control](https://agentprime.io/advisories/tag/access-control.md) - **Published:** 7 Oct 2026 - **Updated:** 7 Oct 2026 - **Reviewed by a person:** No Published by the GitHub Advisory Database at 7 Oct 2026, 20:28 UTC. agentprime has not analysed this yet, so whether it affects any app is not known. ## Critical Critical, because: - CVSS score 9.2: 9.0 or more. How we decide what’s critical: ## Affected packages - `payload` (npm): affected `>=3.0.0, <3.90.0 || >=4.0.0-canary.0, <4.0.0-canary.34`; fixed in `3.90.0`, `4.0.0-canary.34` ## Machine-written summary Summary written by Claude Haiku from the source advisory. Not reviewed by a person. > The npm package payload, versions from 3.0.0 before 3.90.0 and from 4.0.0-canary.0 before 4.0.0-canary.34, can include unintended values in the authentication token issued at login under certain field configurations. The source says an installation is affected when it configures a custom field option that maps a field to a reserved authentication claim name; the source does not describe what an attacker can do with this beyond that. Upgrade payload to 3.90.0 or 4.0.0-canary.34, as no complete workaround is given. Written 31 Oct 2026. ## Not analysed yet We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check. ## Severity and exploitation - 9.2 Critical, CVSS 4.0: `CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N`, from CNA (GitHub_M) - **CISA KEV:** Not listed. - **EPSS:** 0.0055, the 46th percentile, on 11 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days. ## Timeline - 31 Oct 2026, 13:33 UTC: First seen by agentprime - 31 Oct 2026, 13:33 UTC: [Confirmed by OSV](https://osv.dev/vulnerability/GHSA-66wr-7vmr-p5jq) ## Sources - [GitHub Advisory Database: GHSA-66wr-7vmr-p5jq](https://github.com/advisories/GHSA-66wr-7vmr-p5jq) - [OSV: GHSA-66wr-7vmr-p5jq](https://osv.dev/vulnerability/GHSA-66wr-7vmr-p5jq) - - - - - Facts on this page come from the GitHub Advisory Database (CC-BY 4.0), OSV and the other sources listed, as published. We don’t reproduce full advisory descriptions, which can contain exploit code. ## Check whether this affects you A Match means an installed version is in the affected range above. Most don’t affect the app; agentprime hasn’t analysed this one yet. - With the agentprime MCP server (), ask your agent to check the project: `check_lockfile` sends a lockfile, `check_packages` a list of installed packages, and both return the Matches and the upgrades that clear them. `get_advisory` returns this record. Setup: - In a browser: reads your lockfile in the browser, never uploading it. - Whether it touches your code, with file and line: the Claude Code plugin, - As JSON: , or `POST https://api.agentprime.io/v1/match` with your packages () --- The web page: . Everything for agents: .