Upgrade SAP Cloud SDK for Python to version 0.45.2 or later. CVE-2026-89111 is a critical OAuth2 server-side request forgery (SSRF) flaw in versions below 0.45.2. In the affected multi-tenant BTP application scenario, an attacker who controls tenant_subdomain can redirect an OAuth2 token request to an attacker-controlled server and expose client credentials.
SAP’s October 13, 2026 Security Patch Day bulletin rates the issue Critical with a CVSS score of 10.0. If an immediate upgrade is impossible, validate tenant_subdomain against an allowlist of registered tenant subdomains before passing it to any SDK call.
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What is CVE-2026-89111?
CVE-2026-89111 is an OAuth2 server-side request forgery vulnerability in the SAP Cloud SDK for Python package, commonly identified as sap-cloud-sdk. The affected use case is a multi-tenant SAP Business Technology Platform application that passes a user- or request-controlled tenant_subdomain value into the SDK’s OAuth2 flow.
SSRF occurs when a server makes an outbound request to a destination chosen by an attacker. Here, the manipulated destination can receive an OAuth2 token request. The request may contain the application’s client credentials, so the consequence is credential exfiltration rather than merely an unexpected network connection.
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The advisory describes the weakness as CWE-918. It does not establish that every SAP product, every SAP deployment, or every application using OAuth2 is affected. Exposure depends on the named Python package, its deployed version, and whether an attacker can control the relevant parameter in the application.
At-a-glance facts
| Item | What is established |
|---|---|
| Identifier | CVE-2026-89111 |
| Package | SAP Cloud SDK for Python (sap-cloud-sdk) |
| Weakness | CWE-918, server-side request forgery |
| Affected releases | Versions below 0.45.2 |
| Patched release | 0.45.2; later releases are also the intended upgrade path |
| SAP severity | Critical |
| CVSS base score | 10.0 |
How does the SAP OAuth2 SSRF attack work?
- Input reaches the application. An attacker supplies or influences a
tenant_subdomainvalue in a request, message, job, or other application-controlled data path. - The value reaches the SDK. The affected SAP Cloud SDK for Python code uses that value when constructing the OAuth2 token-request destination for a tenant.
- The destination is redirected. A malicious subdomain can cause the server-side request to go to infrastructure controlled by the attacker instead of the registered tenant’s authorization endpoint.
- Credentials are sent. The OAuth2 request can expose the client credentials used by the application.
- The attacker gains material to investigate. The advisory describes possible credential exfiltration. What those credentials permit depends on the application’s OAuth2 configuration and downstream authorization.
The CVSS vector records a network attack vector, low attack complexity, no required privileges, no user interaction, changed scope, high confidentiality impact, high integrity impact, and no availability impact: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:N. These ratings describe the vulnerability’s technical severity; they do not prove exploitation in a particular environment.
Which SAP Cloud SDK for Python versions are affected?
SAP’s bulletin and the maintainer advisory identify all versions below 0.45.2 as affected. Version 0.45.2 is the stated patched release. A system name, BTP subaccount, or application label cannot establish exposure by itself; you must verify the package version actually present in the deployed artifact.
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1Fix the driver behind crashes, sound loss and screen glitches2Repair Windows errors before they cause bigger problems3Scan for outdated or missing drivers - takes under a minute| Installed package version | Status | Required action |
|---|---|---|
| Older than 0.45.2 | Affected | Upgrade to 0.45.2 or later, or apply the documented allowlist workaround until you can upgrade |
| 0.45.2 | Patched version named by the advisory | Confirm that this is the version running in every production artifact |
| Later than 0.45.2 | Beyond the stated fixed version | Keep the dependency maintained through your normal update process |
Check lockfiles, build manifests, container layers, virtual environments, and serverless deployment bundles. It is common for a development environment to show a newer dependency while a production image still contains an older one.
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How can you determine whether an application is exposed?
1. Inventory applications that use the package
Search Python service repositories, dependency manifests, image build files, and deployment pipelines for sap-cloud-sdk. Include worker processes, scheduled jobs, and separate tenant-facing services, not just the primary web application.
2. Verify the installed version
Use the package-management method that matches the application’s build process. For a pip-managed environment, an example check is:
python -m pip show sap-cloud-sdk
python -m pip freeze | grep sap-cloud-sdkFor a container, run the check inside the image or inspect the generated dependency lock and image build output. The decisive value is the version deployed at runtime, not the version on a developer workstation.
3. Trace tenant_subdomain
Identify every place the parameter enters the application and every SDK call that receives it. Treat values from HTTP parameters, headers, uploaded data, queues, tenant metadata, and administrative tools as untrusted until they are checked against an authoritative tenant registry.
4. Check all deployment variants
Review production, staging, disaster-recovery, regional, and customer-specific images. A vulnerable worker or rarely used endpoint can still hold credentials that matter to the broader landscape.
5. Do not infer compromise from version alone
An affected version means the code is vulnerable under the described input conditions. The available advisories do not report a prevalence figure, exploitation campaign, or confirmed compromise in any specific deployment.
What is the recommended fix?
Upgrade affected installations to SAP Cloud SDK for Python 0.45.2 or later through the project’s ordinary dependency review and deployment process.
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- Record the current state. Capture the deployed version, image digest or build identifier, affected services, and the OAuth2 clients they use.
- Update the dependency. Change the direct requirement or lockfile to 0.45.2 or a later maintained release. If your organization uses a constraints file, update that file rather than only changing a local environment.
- Rebuild every artifact. Recreate virtual environments, containers, serverless bundles, and offline wheels so an old cached package is not silently retained.
- Test tenant routing. Exercise normal single-tenant and multi-tenant authentication paths in a non-production environment. Verify that legitimate registered subdomains continue to obtain tokens and that invalid values are rejected before an outbound request.
- Deploy with your normal controls. Use code review, automated tests, staged rollout, and rollback safeguards appropriate to the service.
- Verify at runtime. After deployment, confirm the running package version from the service or image and review startup or deployment logs for the expected artifact.
Do not assume that applying a general SAP platform update automatically changes a separately managed Python dependency. The fixed-version instruction applies to the named package.
What is the temporary tenant_subdomain SSRF mitigation?
If an immediate upgrade is not possible, implement the advisory’s workaround: allow only registered tenant subdomains before passing the value to an SDK call.
Properties of a safe allowlist
- Build it from an authoritative inventory of tenants your application is permitted to serve.
- Compare the supplied value with an exact, canonical entry rather than accepting arbitrary suffixes or partial matches.
- Reject empty, malformed, encoded, or unexpected values before any SDK operation.
- Fail closed when the tenant record is missing or the allowlist cannot be loaded.
- Keep the list under controlled change management and log additions, removals, and rejected attempts.
- Apply the check at every code path that can invoke the SDK, including background jobs and administrative tools.
A minimal pattern is:
REGISTERED_SUBDOMAINS = {'tenant-a', 'tenant-b'}
if tenant_subdomain not in REGISTERED_SUBDOMAINS:
raise ValueError('Unregistered tenant subdomain')
# Pass tenant_subdomain to the SDK only after this check.This example illustrates the validation boundary; adapt it to your tenant registry, error handling, and application framework. An allowlist reduces the vulnerable input path but does not replace upgrading the package.
What should you do if credentials may have been exposed?
The advisory describes possible OAuth2 client-credential exfiltration when an attacker controls the parameter. If your logs, telemetry, or application review show that an untrusted value reached the affected flow, activate your incident procedure and involve the teams that own the OAuth2 client and downstream services.
- Preserve relevant application, proxy, identity-provider, and BTP logs before retention windows remove them.
- Determine which tenant value was supplied, which service handled it, and which OAuth2 client was used.
- Look for outbound token requests to destinations that are not part of the registered tenant configuration.
- Assess what scopes and downstream permissions the client had.
- Follow your credential-owner policy for revocation, replacement, and notification if exposure is plausible.
- Continue with the package upgrade and the input allowlist while the review is in progress.
Do not state that a deployment was compromised solely because it ran an affected version. The published materials identify a potential credential-exfiltration path, not a confirmed incident in every installation.
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Why is the vulnerability rated Critical with CVSS 10.0?
SAP’s October 2026 bulletin gives the issue a Critical rating and a CVSS score of 10.0. The maintainer advisory also gives a CVSS 3.1 base score of 10.0. The vector explains the score:
| Metric | Value | Meaning in this advisory |
|---|---|---|
| Attack vector | Network | The attack is delivered through a reachable application input path |
| Attack complexity | Low | No unusual conditions are specified once the input is controllable |
| Privileges required | None | The vector does not require an authenticated account |
| User interaction | None | No separate user action is required |
| Scope | Changed | Impact can cross from the vulnerable application into another security authority |
| Confidentiality | High | Client credentials may be disclosed |
| Integrity | High | Misused credentials could enable unauthorized changes within their permissions |
| Availability | None | The stated scoring does not assign an availability impact |
CVSS is a prioritization measure, not a prediction of how many systems are affected or whether exploitation is occurring in the wild.
How does SAP’s Security Patch Day guidance apply?
SAP says Security Patch Day is scheduled for the second Tuesday of each month and advises customers to prioritize security corrections. SAP also notes that high- and very-high-severity fixes can depend on support-package age and maintenance status. Those lifecycle considerations matter for SAP landscapes, but they do not alter the specific instruction for this Python package: versions below 0.45.2 should be upgraded.
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Does this affect every SAP OAuth2 integration?
No. The published description is limited to the SAP Cloud SDK for Python package and the multi-tenant application context in which an attacker can control tenant_subdomain. It does not name other SAP SDKs, programming languages, products, or deployments as affected. Verify the actual dependency and data flow before expanding the scope of an incident or remediation campaign.
Can a firewall or generic security appliance fix the issue?
There is no evidence that a particular hardware product, security appliance, or commercial service is the direct fix. Remediation is software-based: upgrade the dependency and, temporarily, enforce the tenant-subdomain allowlist. Network monitoring can support detection, but it does not remove the vulnerable code path or guarantee that credentials cannot be sent to an attacker-controlled destination.
What should security teams record for audit purposes?
- The services and deployment artifacts found to use SAP Cloud SDK for Python.
- The version observed in each running environment.
- The date and change record for upgrading to 0.45.2 or later.
- The authoritative source and owner of the registered tenant-subdomain allowlist.
- Tests showing that unregistered values are rejected before an SDK call.
- Any investigation into suspicious outbound OAuth2 requests or possible credential exposure.
Keep the records specific to the application and artifact. A broad statement such as “the SAP system is patched” does not demonstrate that every Python package instance is fixed.
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