CVE-2026-6477: Use of inherently dangerous function PQfn(..., result_is_int=0, ...) in PostgreSQL libpq lo_export(), lo_read(

This month

HIGH 8.8UPGRADE

CVE-2026-6477 is a high-severity flaw (CVSS 8.8) affecting postgresql. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Use 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

Why this priority

High severity

A fixed release or distro patch exists.

Risk facts

CVSS score	8.8 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	Required
EPSS exploit chance	0.5% (top 61%)
CISA exploited list	No
Weakness	CWE-242, CWE-120
Published	2026-05-14
Last modified	2026-08-25

Publisher (CNA): PostgreSQL · Vendor: postgresql

Last updated 2026-08-25 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-05-14 14:16 UTCPublished CVE record published
2026-08-25 13:19 UTCUpdated Record last modified

postgresql postgresql UPGRADE

Affected: < 14.23 · >= 15.0 and < 15.18 · >= 16.0 and < 16.14 · >= 17.0 and < 17.10 · >= 18.0 and < 18.4

Fixed in: 14.23, 15.18, 16.14, 17.10, 18.4

Safe to downgrade to: a release before 15.0

1. Check installed version

apt-cache policy postgresql || rpm -q postgresql || postgresql --version

2. UPGRADE to 14.23 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade postgresql

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade postgresql

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

3. If no update is available yet, DOWNGRADE to a release before 15.0 (Debian / Ubuntu)

apt-cache madison postgresql sudo apt install postgresql=<VERSION_BEFORE_15.0> sudo apt-mark hold postgresql

3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list postgresql sudo dnf downgrade postgresql-<VERSION_BEFORE_15.0> sudo dnf versionlock add postgresql

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

Advisories and coverage

Official advisories

AlmaLinux Errata: [ALSA-2026:44308] Important: libpq security update 2026-07-23

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-6477?

postgresql: upgrade to 14.23, 15.18, 16.14, 17.10, 18.4. Exact commands for each OS are on this page.

Is CVE-2026-6477 being exploited?

CVE-2026-6477 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-6477 affect?

CVE-2026-6477 affects postgresql. Severity is high (CVSS 8.8). Use 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-larg

How urgent is CVE-2026-6477?

Priority 41/100. High severity

Software pages

PostgreSQL vulnerabilities

Related CVEs

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References

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