CVE-2026-120058 in psqlODBC
Summary
by MITRE • 11/02/2026
psqlODBC sizes its row cache from the column count of a cursor's first result, but recomputes the column count from each later FETCH reply without checking that it matches. A server not trusted under current SSL settings can answer a later FETCH with more columns and make the driver write tuple records past the end of the heap allocation. A keyset reply with fewer columns than the key fields also underflows the unsigned field count. This is reachable with UseDeclareFetch enabled. Versions before psqlODBC 18.00.0006 are affected.
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Analysis
by VulDB Data Team • 11/02/2026
The vulnerability in psqlODBC stems from a fundamental flaw in how the driver manages memory allocation for row caching during cursor operations, specifically when the UseDeclareFetch option is enabled. Under normal operation, the driver initializes its internal row cache structure based on the column count returned by the first result set of a cursor query. This initial size determination establishes the bounds for subsequent data retrieval operations. However, the implementation fails to validate that this allocated buffer size remains consistent with the metadata provided in later FETCH replies from the database server. Instead of verifying that the number of columns in each incoming row matches the initially established count, the driver blindly trusts the column count reported by the server and proceeds to write tuple records into memory based on that unverified value. This lack of input validation creates a critical boundary condition where the integrity of heap-allocated structures is compromised if the server's response deviates from expectations.
The operational impact manifests in two distinct ways depending on whether the subsequent FETCH reply contains more or fewer columns than expected. When a malicious or misconfigured database server responds to a later FETCH request with a higher number of columns than were present in the initial result set, the driver attempts to write data into memory locations beyond the end of the originally allocated heap buffer. This results in an out-of-bounds write vulnerability, which can lead to heap corruption, arbitrary code execution if specific memory layouts are exploited, or application crashes due to segmentation faults. Conversely, when a keyset reply contains fewer columns than required for the defined key fields, the driver underflows an unsigned field count variable. This integer underflow can cause severe miscalculations in buffer sizes and loop iterations, potentially leading to access violations or further memory corruption as the driver attempts to process data structures with invalid dimensions.
This vulnerability is particularly dangerous because it relies on the interaction between the client-side ODBC driver and a database server that may not be fully trusted under current SSL settings. If an attacker can intercept traffic or control the response from a compromised or rogue PostgreSQL instance, they can craft specific FETCH responses to trigger these memory safety violations. The requirement for UseDeclareFetch being enabled narrows the attack surface slightly but does not eliminate it, as this mode is often used in production environments to manage large result sets efficiently. Versions prior to psqlODBC 18.00.0006 are susceptible to both the heap overflow and integer underflow conditions described above.
From a classification perspective, this issue aligns with CWE-787: Out-of-bounds Write, as it involves writing data beyond allocated memory boundaries due to insufficient validation of input dimensions. Additionally, the integer underflow aspect relates closely to CWE-190: Integer Overflow or Wraparound, which can lead to unexpected behavior in size calculations and buffer management. In terms of attack vectors, this vulnerability could be leveraged within an ATT&CK framework context as part of a lateral movement or privilege escalation technique if exploited on a system with elevated privileges, although it primarily serves as a potential initial code execution vector via memory corruption.
Mitigation strategies should prioritize immediate upgrading to psqlODBC version 18.00.0006 or later, where the developers have implemented proper validation checks for column counts in FETCH replies against the initially allocated row cache size. Until an upgrade is feasible, administrators can mitigate risk by disabling UseDeclareFetch if it is not strictly necessary for their application's performance requirements, thereby avoiding the code path that contains this flaw. Furthermore, ensuring strict SSL/TLS configurations and verifying server certificates helps prevent man-in-the-middle attacks where a rogue server might attempt to exploit this vulnerability through crafted responses. Regular patching of database connectivity components remains essential to maintaining the integrity of data processing pipelines against such memory safety violations.