PostgreSQL libpq lo_* functions let server superuser overwrite client stack memory

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Summary

CVECVE-2026-6477
StatePUBLISHED
AssignerPostgreSQL
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-05-14 14:16:25 UTC
Updated2026-05-18 15:03:26 UTC
DescriptionUse of inherently dangerous function PQfn(..., result_is_int=0, ...) in PostgreSQL libpq lo_export(), lo_read(), lo_lseek64(), and lo_tell64() functions allows the server superuser to overwrite a client stack buffer with an arbitrarily-large response. Like gets(), PQfn(..., result_is_int=0, ...) stores arbitrary-length, server-determined data into a buffer of unspecified size. Because both the \lo_export command in psql and pg_dump call lo_read(), the server superuser can overwrite pg_dump or psql stack memory. Versions before PostgreSQL 18.4, 17.10, 16.14, 15.18, and 14.23 are affected.

Risk And Classification

Primary CVSS: v3.1 8.8 HIGH from f86ef6dc-4d3a-42ad-8f28-e6d5547a5007

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

EPSS: 0.000470000 probability, percentile 0.144780000 (date 2026-05-25)

Problem Types: CWE-242 | CWE-242 Use of Inherently Dangerous Function

VersionSourceTypeScoreSeverityVector
3.1f86ef6dc-4d3a-42ad-8f28-e6d5547a5007Secondary8.8HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
3.1CNACVSS8.8HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
Required
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

NVD Known Affected Configurations (CPE 2.3)

TypeVendorProductVersionUpdateEditionLanguage
Application Postgresql Postgresql All All All All

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Na PostgreSQL affected 18 18.4 rpm Not specified
CNA Na PostgreSQL affected 17 17.10 rpm Not specified
CNA Na PostgreSQL affected 16 16.14 rpm Not specified
CNA Na PostgreSQL affected 15 15.18 rpm Not specified
CNA Na PostgreSQL affected 14.23 rpm Not specified

References

ReferenceSourceLinkTags
www.postgresql.org/support/security/CVE-2026-6477 f86ef6dc-4d3a-42ad-8f28-e6d5547a5007 www.postgresql.org Patch, Vendor Advisory
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis

Vendor Comments And Credit

Discovery Credit

CNA: The PostgreSQL project thanks Yu Kunpeng and Martin Heistermann for reporting this problem. (en)

Additional Advisory Data

Workarounds

CNA: use PQexecPrepared(), not PQfn(..., result_is_int=0, ...) or its lo_* wrappers

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