CVE-2021-3445
Description
A flaw was found in libdnf's signature verification functionality. This flaw allows an attacker to achieve code execution if they can alter the header information of an RPM package and then trick a user or system into installing it. The highest risk of this vulnerability is to confidentiality, integrity, as well as system availability.
Statement
The exploitation of this flaw requires RPM's package verification level to be set to "digest" or "none". In addition, to exploit this flaw, an attacker must either compromise an RPM repository or convince an administrator to install an untrusted RPM. It is strongly recommended to only use RPMs from trusted repositories.
Mitigation
A mitigation for this flaw is to set %_pkgverify_level all` or `%_pkgverify_level signature` in `/etc/rpm/macros`.
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 | 6.4 | 7.5 | N/A |
| Attack Vector | Network | Network | N/A |
| Attack Complexity | High | High | N/A |
| Privileges Required | High | None | N/A |
| User Interaction | Required | Required | N/A |
| Scope | Unchanged | Unchanged | N/A |
| Confidentiality | High | High | N/A |
| Integrity Impact | High | High | N/A |
| Availability Impact | High | High | N/A |
Vector
Red Hat: CVSS:3.1/AV:N/AC:H/PR:H/UI:R/S:U/C:H/I:H/A:H
NVD: CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H
Red Hat CVSS v3 Score Explanation
We marked AC:H because the package verification level must be set to "digest" or "none", which is out of an attacker's control. Additionally, an RPM would need to be placed into a repository, so an attacker would need to compromise an RPM repository or perform a Man-in-the-middle attack (in case of no TLS) to modify the RPM first, or trick a system administrator into installing it from another source. PR:H because the above scenarios require elevated privileges to perform.
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.
Acknowledgements
Red Hat would like to thank Demi M. Obenour for reporting this issue.
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