high CVSS 7.5 EPSS 0.60%

CVE-2026-6479·PostgreSQL vulnerability

Uncontrolled recursion in PostgreSQL SSL and GSS negotiation allows an attacker able to connect to a PostgreSQL AF_UNIX socket to achieve sustained denial of service. If SSL and GSS are both disabled, an attacker can do the same via access to a PostgreSQL TCP socket. Versions before PostgreSQL 18.4, 17.10, 16.14, 15.18, and 14.23 are affected.

Severity
high
Software
PostgreSQL
Fixed in
18.4
Published

How likely is exploitation

FIRST's Exploit Prediction Scoring System puts the probability of this CVE being exploited in the next 30 days at 0.60% — higher than 47% of all published CVEs. EPSS is an independent forecast of exploitation, not a severity rating: it says nothing about how much damage a successful attack does, which is what a CVSS score measures.

Read the two together. CVE-2026-6479 scores 7.5 on CVSS, so a successful attack would be serious — but at 0.60%, almost nobody is currently attempting it. That is a different situation from a flaw under mass exploitation, and it is usually the difference between patching on your next maintenance window and patching tonight.

Affected versions

From: 18.0

Until: 18.4

Fixed in: 18.4

How to fix this CVE

Upgrade PostgreSQL to version 18.4 or later to patch a recursion flaw in the SSL/GSS negotiation handler that enables denial-of-service attacks. Organizations running PostgreSQL 18.0–18.3 should prioritize this update immediately, especially if Unix socket or unauthenticated TCP access is permitted. Apply the patch during a maintenance window to prevent service interruption.

sudo dnf update postgresql-server-18-18.4

Defensia detects this vulnerability

How to check if you are affected

  1. Run `psql --version` or query `SELECT version();` in PostgreSQL to confirm the installed version number.
  2. Check if PostgreSQL is configured to accept connections via AF_UNIX sockets by inspecting `/var/run/postgresql/` and verifying the presence of socket files.
  3. Review PostgreSQL logs in `/var/log/postgresql/` for repeated connection errors, protocol negotiation failures, or messages indicating abnormal SSL/GSS negotiation attempts.
  4. After patching, verify the fix by running `psql --version` again and confirm the version is 18.4 or higher, then restart PostgreSQL with `sudo systemctl restart postgresql`.

FAQ

What is CVE-2026-6479?

CVE-2026-6479 is a denial-of-service vulnerability in PostgreSQL's SSL and GSS authentication negotiation code that permits unbounded recursion, allowing attackers to exhaust server resources and crash the database service.

Is CVE-2026-6479 being actively exploited?

No, this vulnerability is not listed on CISA's Known Exploited Vulnerabilities (KEV) catalog and no public exploits have been disclosed.

What versions of PostgreSQL are affected by CVE-2026-6479?

PostgreSQL versions 18.0 through 18.3 are vulnerable. The vulnerability is also present in earlier branches (17.x, 16.x, 15.x, 14.x) but only version 18 through 18.4 is specified in this CVE scope.

How do I check if my server is vulnerable to CVE-2026-6479?

Run `psql -U postgres -c 'SELECT version();'` to retrieve the PostgreSQL version. If the output shows a version between 18.0 and 18.3, your installation is vulnerable.

Does Defensia detect CVE-2026-6479?

Yes — Defensia's CVE advisory scanner compares installed package versions against the NVD database. If PostgreSQL is installed on a monitored server, CVE-2026-6479 will appear in your dashboard with remediation steps.

Related PostgreSQL CVEs

CVE-2026-15742CVSS 8.8Integer wraparound in PostgreSQL fuzzystrmatch allows a user to direct writes to a huge range of addresses, executing arbitrary code as the operating system user running the database, via extreme inputs to SQL function levenshtein() or levenshtein_less_equal(). Versions before PostgreSQL 18.6, 17.11, 16.15, 15.19, and 14.24 are affected.
CVE-2026-14670CVSS 8.8Heap buffer overflow in PostgreSQL plperl return of a tied hash allows the function owner to execute arbitrary code as the operating system user running the database, via a crafted function body. Versions before PostgreSQL 18.6, 17.11, 16.15, 15.19, and 14.24 are affected.
CVE-2026-14669CVSS 8.8Heap buffer overflow in PostgreSQL to_char(timestamptz) allows the party choosing the timezone to execute arbitrary code as the operating system user running the database, via a long POSIX timezone abbreviation. Versions before PostgreSQL 18.6, 17.11, 16.15, 15.19, and 14.24 are affected.
CVE-2026-14671CVSS 8.8Type confusion in PostgreSQL module "refint" allows an object creator to execute arbitrary code as the operating system user running the database. The fix for this emerged as a non-security bug report, and the fix appear in the git repository with subject "refint: Remove plan cache.", without a CVE number. Versions before PostgreSQL 18.6, 17.11, 16.15, 15.19, and 14.24 are affected.
CVE-2026-14664CVSS 8.8Heap buffer overflow in PostgreSQL regexp allows the query author to execute arbitrary code as the operating system user running the database, via text that would not pass encoding validation. This shares heritage with CVE-2026-2006, but this case involved unanticipated data growth when round-tripped through pg_wchar. Versions before PostgreSQL 18.6, 17.11, 16.15, 15.19, and 14.24 are affected.

References

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