CVE-2021-28091
Description
An XML Signature Wrapping (XSW) vulnerability was found in Lasso. This flaw allows an attacker to modify a valid SAML response to include an unsigned SAML assertion, which may be used to impersonate another valid user recognized by the service using Lasso. The highest threat from this vulnerability is to data confidentiality and integrity as well as service availability.
Statement
Lasso is provided in Red Hat Enterprise Linux 7, and 8 only as a dependency of mod_auth_mellon, without development files. The way mod_auth_mellon uses Lasso makes it not vulnerable to this flaw, because SAML responses are additionally validated to have exactly one assertion, thus it is not possible for an attacker to include an unsigned SAML assertion after a signed valid one. For this reason this flaw has been rated as Moderate on Red Hat Enterprise Linux 8.
Red Hat Enterprise Linux 7 also provides a lasso-python package that can be used to create python applications that use Lasso, however Red Hat only ships ipsilon which uses it. Ipsilon does not use the vulnerable functions of Lasso. Considering the presence of lasso-python in Red Hat Enterprise Linux 7, this flaw has been rated as Important there.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 8.8 | 7.5 | N/A |
| Attack Vector | Network | Network | N/A |
| Attack Complexity | Low | Low | N/A |
| Privileges Required | Low | None | N/A |
| User Interaction | None | None | N/A |
| Scope | Unchanged | Unchanged | N/A |
| Confidentiality | High | None | N/A |
| Integrity Impact | High | High | N/A |
| Availability Impact | High | None | N/A |
Vector
Red Hat: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
NVD: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
Red Hat CVSS v3 Score Explanation
Privileged Required set to Low (PR:L) because to trigger the flaw the attacker must have a valid SAML assertion of an already recognized user. Confidentiality and Availability both set to High (C:H/A:H) given that this flaw could be abused to impersonate an admin account in some cases.
Understanding the Weakness (CWE)
Access Control,Integrity,Confidentiality
Technical Impact: Gain Privileges or Assume Identity; Modify Application Data; Execute Unauthorized Code or Commands
An attacker could gain access to sensitive data and possibly execute unauthorized code.
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