CVE-2021-28091
説明
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.
詳細
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.
CVSS (Common Vulnerability Scoring System) のスコアの詳細
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 スコアの内訳
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| ベーススコア | 8.8 | 7.5 | N/A |
| 攻撃ベクトル | Network | Network | N/A |
| 攻撃の複雑さ | Low | Low | N/A |
| 必要な権限 | Low | None | N/A |
| ユーザー関与レベル | None | None | N/A |
| 範囲 | Unchanged | Unchanged | N/A |
| 機密性 | High | None | N/A |
| 完全性への影響 | High | High | N/A |
| 可用性への影響 | High | None | N/A |
ベクトル
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 スコアの説明
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.
脆弱性の原因 (CWE) の理解
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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