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CVE-2026-14678 is a buffer over-read vulnerability identified in the PostgreSQL relational database system. The flaw resides within the `pg_trgm` extension, specifically in the index `picksplit` function. The `pg_trgm` module provides functions and operators for determining the similarity of alphanumeric text based on trigram matching, and is commonly used to support fast full-text search capabilities via Generalized Inverted Indexes (GIN) and GiST indexes.
The `picksplit` function is an internal component of PostgreSQL’s indexing mechanism. When a new index entry is added and an index page becomes full, the `picksplit` function is called to decide how to split the page’s contents across two new pages. For trigram indexes, this function processes the data present in a heap buffer. Due to improper bounds checking, the function can read data past the end of the allocated heap buffer. This out-of-bounds read can occur when the function attempts to access memory locations that are adjacent to, but outside of, the legitimate buffer.
This vulnerability is not a classic buffer overflow that overwrites memory; it is an over-read that leaks information. By carefully crafting input data and observing the resulting index split choices, an authenticated attacker with table maintenance privileges could potentially infer the values of nearby memory contents. This information leakage is limited and occurs through a “lossy signal”, meaning the attacker can only deduce partial or statistical information about the memory layout, rather than reading arbitrary memory regions directly. The attack requires the user to have the ability to create or modify tables and indexes, making it a local, authenticated attack vector.
The issue affects all PostgreSQL versions prior to the patched releases: 18.5, 17.11, 16.15, 15.19, and 14.24. It is worth noting that PostgreSQL version 18.5 was never officially released due to a regression discovered during the development cycle; the actual fixed version for the 18.x branch is 18.6. The vulnerability is classified with a CVSS v3.1 base score of 4.3 (MEDIUM) with the vector string CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N, indicating a low impact on confidentiality with no impact on integrity or availability. The attack complexity is low, requires low privileges, and can be executed over the network.
DailyCVE Form:
Platform: PostgreSQL
Version: <18.5,17.11,16.15,15.19,14.24
Vulnerability : Buffer Over-read
Severity: MEDIUM (4.3)
date: 2026-08-13
Prediction: Patch already released
What Undercode Say:
The vulnerability is rooted in unsafe memory access patterns within the `pg_trgm` index’s split logic. Administrators should prioritize upgrading to the latest patched versions to mitigate the risk of information disclosure.
Check current PostgreSQL version psql -V For Debian/Ubuntu-based systems sudo apt-get update sudo apt-get install --only-upgrade postgresql For RHEL/CentOS/Fedora-based systems sudo dnf update postgresql-server For manual compilation or source installations Download and apply the latest patches from the official repository
Exploit: (Educational Purposes!)
Exploitation of this vulnerability requires authenticated database access with table creation or modification privileges. The following conceptual steps illustrate a potential attack vector:
1. Environment Setup: The attacker creates a test database and enables the `pg_trgm` extension.
2. Crafted Input: A table is created with a text column, and a trigram index (GIN or GiST) is built on that column.
3. Data Insertion: Specially crafted strings are inserted into the table to trigger the index split operation.
4. Triggering the Flaw: By forcing the index to split, the vulnerable `picksplit` function is invoked, reading past the allocated heap buffer.
5. Information Inference: The attacker observes the index split outcomes (which tuples go to which new page). By correlating the split decisions with the crafted input, the attacker infers the values of adjacent memory, potentially revealing sensitive data from other database processes or system information.
-- Example of enabling the extension and creating a table
CREATE EXTENSION IF NOT EXISTS pg_trgm;
CREATE TABLE test_table (data TEXT);
CREATE INDEX trgm_idx ON test_table USING GIN (data gin_trgm_ops);
-- Inserting crafted data to potentially trigger the flaw
INSERT INTO test_table VALUES ('crafted_string_to_trigger_split');
Protection:
The primary and only reliable protection against CVE-2026-14678 is to upgrade to a patched version of PostgreSQL. All supported versions have received fixes: 18.6, 17.11, 16.15, 15.19, and 14.24. Users of the 18.x branch must upgrade to 18.6, as 18.5 was never released.
If an immediate upgrade is not possible, consider the following interim measures:
– Restrict User Privileges: Limit database user permissions to the minimum necessary. Only grant `CREATE TABLE` and index creation privileges to trusted users, as the attack requires these capabilities.
– Monitor Database Activity: Implement monitoring for unusual index creation or modification patterns that could indicate an attempted exploit.
– Disable pg_trgm: If the `pg_trgm` extension is not required for your application, consider removing it (DROP EXTENSION pg_trgm;). However, this will break any functionality that depends on trigram-based text search.
Impact:
The impact of this vulnerability is considered limited due to the following factors:
– Authentication Required: An attacker must have valid database credentials with the necessary privileges to create or modify tables and indexes.
– Low Information Leakage: The vulnerability is an over-read, not an overwrite. It allows inference of limited memory values through a lossy signal, rather than direct, arbitrary memory reads.
– No Integrity or Availability Impact: The CVSS score reflects that there is no impact on the integrity or availability of the system. The database continues to function normally; the flaw only presents a risk of information disclosure.
Despite the limited impact, the vulnerability represents a breach of the principle of least privilege and could be a stepping stone for more sophisticated attacks. Given the widespread use of PostgreSQL, it is strongly recommended that all users apply the available security updates to maintain a robust security posture.
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Sources:
Reported By: nvd.nist.gov
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