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

published 2026-06-17 4 mo ago modified 2026-10-26 14 d ago also GHSA-4j9m-h44m-2hv8 , EUVD-2026-37821

cvss: 1.9; version 3.1, CNA
cisa kev: Not listed; not in CISA's catalog
epss: 0.0%; EPSS 0.0% chance of exploitation in 30 days, percentile 0%
public exploits: 0; none known

Steeltoe is an open source project that provides a collection of libraries that helps users build cloud-native applications. In Steeltoe.Configuration.Encryption 4.0.0 through 4.1.0, 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. Steeltoe.Configuration.Encryption version 4.2.0 patches the issue.

Patch / fix

fixed in 1 links 1

nuget Steeltoe.Configuration.Encryption 4.2.0

github.com/SteeltoeOSS/Steeltoe@6cfee5c commit

CISA SSVC

Exploitation: none
Automatable: no
Technical impact: partial
Assessed: 4 mo ago (2026-06-18)

Exploit prediction

0.05% chance of exploitation in the next 30 days, higher than 0% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by	version	score	vector
CNA	3.1	1.9	CVSS:3.1/AV:L/AC:H/PR:H/UI:N/S:U/C:L/I:N/A:N
GitHub	3.1	1.9	CVSS:3.1/AV:L/AC:H/PR:H/UI:N/S:U/C:L/I:N/A:N

Affected packages

ecosystem	package	affected	fixed in
nuget	Steeltoe.Configuration.Encryption	>=4.0.0, <4.2.0	4.2.0

Affected products

SteeltoeOSS Steeltoe.Configuration.Encryption

Classification

Weakness

CWE-256 Plaintext Storage of a Password
CWE-327 Use of a Broken or Risky Cryptographic Algorithm

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

Summary