CVE-2023-51764
Description
A flaw was found in some SMTP server configurations in Postfix. This flaw allows a remote attacker to break out email message data to "smuggle" SMTP commands and send spoofed emails that pass SPF checks.
Out of the box, Postfix targets to accommodate older clients with faulty SMTP implementations due to which restrictions are not enforced in the default configuration. Appropriate mitigation strategies are mentioned in the appropriate section below.
Statement
The impact is considered Moderate likely due to certain conditions required for successful exploitation, such as specific server configurations.
Mitigation
This flaw can be PARTIALLY mitigated via the following options in the main.cf:
smtpd_data_restrictions = reject_unauth_pipelining
smtpd_discard_ehlo_keywords = chunking, silent-discard
Please note this only blocks the misuse of SMTP command pipelining, but does not address message pipelining nor malformed line endings. The only fix for these issues are via package updates.
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 | 5.3 | 5.3 | N/A |
| Attack Vector | Network | Network | N/A |
| Attack Complexity | Low | Low | N/A |
| Privileges Required | None | None | N/A |
| User Interaction | None | None | N/A |
| Scope | Unchanged | Unchanged | N/A |
| Confidentiality | None | None | N/A |
| Integrity Impact | Low | Low | N/A |
| Availability Impact | None | None | N/A |
Vector
Red Hat: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
NVD: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
Understanding the Weakness (CWE)
Access Control
Technical Impact: Bypass Protection Mechanism
In some cases, injectable code controls authentication; this may lead to a remote vulnerability.
Access Control
Technical Impact: Gain Privileges or Assume Identity
Injected code can access resources that the attacker is directly prevented from accessing.
Integrity,Confidentiality,Availability
Technical Impact: Execute Unauthorized Code or Commands
When a product allows a user's input to contain code syntax, it might be possible for an attacker to craft the code in such a way that it will alter the intended control flow of the product. As a result, code injection can often result in the execution of arbitrary code. Code injection attacks can also lead to loss of data integrity in nearly all cases, since the control-plane data injected is always incidental to data recall or writing.
Non-Repudiation
Technical Impact: Hide Activities
Often the actions performed by injected control code are unlogged.
Frequently Asked Questions
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