CVE-2026-6477
Description
A flaw was found in PostgreSQL libpq. A server superuser can exploit a buffer overflow vulnerability in the PQfn function, which is used by client functions such as lo_export(), lo_read(), lo_lseek64(), and lo_tell64(). This allows the superuser to send an arbitrarily large response, overwriting the client's stack memory, specifically in tools like psql and pg_dump. This could lead to arbitrary code execution on the client system.
Statement
This IMPORTANT buffer overflow in PostgreSQL libpq allows a malicious server superuser to overwrite client stack memory via lo_* functions. Exploitation requires the victim to connect to a compromised or malicious server (UI:R). The scope is changed as the server attack affects the client system. Impact is high to confidentiality, integrity, and availability through potential client-side code execution. Affects versions before 18.4, 17.10, 16.14, 15.18, and 14.23.
Mitigation
Only connect to trusted PostgreSQL servers. Avoid using psql or pg_dump against untrusted or potentially compromised database servers.
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 | 8.4 | N/A | 8.4 |
| Attack Vector | Network | N/A | Network |
| Attack Complexity | Low | N/A | Low |
| Privileges Required | High | N/A | High |
| User Interaction | Required | N/A | Required |
| Scope | Changed | N/A | Changed |
| Confidentiality | High | N/A | High |
| Integrity Impact | High | N/A | High |
| Availability Impact | High | N/A | High |
Vector
Red Hat: CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:C/C:H/I:H/A:H
cve.org: CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:C/C:H/I:H/A:H
Understanding the Weakness (CWE)
Integrity,Confidentiality,Availability
Technical Impact: Modify Memory; Execute Unauthorized Code or Commands
Buffer overflows often can be used to execute arbitrary code, which is usually outside the scope of the product's implicit security policy. This can often be used to subvert any other security service.
Availability
Technical Impact: Modify Memory; DoS: Crash, Exit, or Restart; DoS: Resource Consumption (CPU)
Buffer overflows generally lead to crashes. Other attacks leading to lack of availability are possible, including putting the product into an infinite loop.
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