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CVE-2026-6477 is a client-side stack buffer overflow vulnerability in PostgreSQL's libpq library. The flaw stems from use of the inherently unsafe PQfn() API with result_is_int=0 in large-object related code paths, including lo_export(), lo_read(), lo_lseek64(), and lo_tell64(). For non-integral result types, PQfn() does not receive the size of the caller-provided output buffer, so it cannot validate whether server-supplied response data will fit before copying it. As a result, a malicious PostgreSQL server, or a server superuser controlling responses, can return arbitrarily large data and overwrite stack memory in the client process. Prominent affected client-side paths include the psql \lo_export command and pg_dump, both of which can reach the vulnerable large-object handling routines. Affected versions are PostgreSQL releases before 18.4, 17.10, 16.14, 15.18, and 14.23.
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A vulnerability in PostgreSQL addressed indirectly through upgraded third-party components in Tenable Security Center.
A client-side code execution risk in PostgreSQL's libpq client library caused by unsafe PQfn usage in large-object helper functions, enabling stack memory overwrite in client tools.
A PostgreSQL libpq client-side memory corruption vulnerability in PQfn() where a malicious server can overwrite client memory because output buffer sizes are not validated for non-integral result types.
A PostgreSQL libpq client-side memory corruption vulnerability in PQfn() where a malicious server can overwrite client memory because output buffer size is not provided for non-integral result types.
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Every observed campaign linking this CVE to a named adversary.
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Cross-references every affected SKU, including bundled OEM variants.
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