Steeltoe: OAEP setting silently selects PKCS#1 v1.5 padding

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

1.9 · CVSS:3.1/AV:L/AC:H/PR:H/UI:N/S:U/C:L/I:N/A:N

EPSS

• CVE-2026-50268: 0.05% estimated exploitation activity in the next 30 days; percentile 0.00 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary Configuring encrypt:rsa:algorithm=OAEP does not enable OAEP encryption. Due to an incorrect BouncyCastle transformation string, the OAEP setting selects PKCS#1 v1.5, which is the same algorithm as the DEFAULT setting. Impact Operators who configure encrypt:rsa:algorithm=OAEP to obtain CCA2-secure padding receive PKCS#1 v1.5 instead. Currently, Decrypt() is called only against operator-controlled configuration data, so no exploitable path exists, but any future code path that exposes a decryption oracle would be Bleichenbacher-vulnerable despite the OAEP setting. Migration note Existing {cipher} values produced under the broken OAEP setting were encrypted with PKCS#1 v1.5. The fix makes OAEP use actual OAEP padding, so those values will fail to decrypt after upgrading. Re-encrypt all affected {cipher} values after upgrading.

Published by the source

2 Jul 2026, 20:32 UTC

Last modified by the source

2 Jul 2026, 20:32 UTC

Source last checked

26 Oct 2026, 17:04 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-4j9m-h44m-2hv8

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# Patch Next advisory brief: CVE-2026-50268

Advisory: Steeltoe: OAEP setting silently selects PKCS#1 v1.5 padding
IDs: CVE-2026-50268, GHSA-4j9m-h44m-2hv8
Record: https://patchnext.com/advisories/cve-2026-50268 (revision 1, source checked 26 Oct 2026, 17:04 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Low (CVSS 1.9)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: steeltoe.configuration.encryption 4.2.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- NuGet steeltoe.configuration.encryption: affected >= 4.0.0, <= 4.1.0; fixed in 4.2.0

## Suggested inspection (read-only)
- NuGet steeltoe.configuration.encryption: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on steeltoe.configuration.encryption.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-4j9m-h44m-2hv8 (GitHub-reviewed advisory GHSA-4j9m-h44m-2hv8 lists affected ranges: NuGet steeltoe.configuration.encryption >=4.0.0 <=4.1.0)

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