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CVE ID: CVE-2026-14677
How CVE-2026-14677 Works
CVE-2026-14677 is an integer wraparound vulnerability affecting 32-bit builds of PostgreSQL’s procedural language extensions, specifically PL/Tcl and PL/Perl. The flaw resides in how these extensions handle memory allocation sizes when processing user-defined function bodies.
In 32-bit architectures, integer values are stored in 32-bit registers with a maximum representable value of 2³¹-1 (2,147,483,647). When a calculation intended to determine a memory allocation size exceeds this maximum, the value “wraps around” to a very small number—often zero or a negative value that gets interpreted as a large unsigned integer. This is known as an integer overflow or wraparound (CWE-190).
An authenticated database user with object creation privileges can craft a malicious PL/Tcl or PL/Perl function body that triggers this wraparound condition. The PostgreSQL server, when compiling or executing the function, performs arithmetic on user-controlled input to calculate the buffer size needed. When the calculated size overflows, the server allocates a memory buffer that is significantly smaller than required.
Subsequent write operations to this undersized buffer cause an out-of-bounds write, corrupting adjacent memory structures. An attacker can leverage this memory corruption to overwrite critical server data structures, potentially redirecting execution flow and executing arbitrary code. The executed code runs with the privileges of the operating system user that owns the PostgreSQL process—typically the `postgres` user, which often has extensive system access.
The vulnerability is particularly concerning because it requires only low privileges (object creation) and no user interaction, with a network-accessible attack vector. CVSS v3.1 base score is 8.8 (HIGH) with Confidentiality, Integrity, and Availability impacts all rated HIGH. This vulnerability resembles CVE-2026-6473, which addressed similar integer wraparound issues in other PostgreSQL server features. The PostgreSQL development team has since backported fixes using safer allocation functions like `palloc_array()` to prevent overflow conditions.
DailyCVE Form:
Platform: PostgreSQL 32-bit
Version: <18.5,<17.11,<16.15,<15.19,<14.24
Vulnerability: Integer wraparound/OOB write
Severity: HIGH (CVSS 8.8)
Date: 2026-08-13
Prediction: Patch already available (2026-08-13)
What Undercode Say:
Analytics and forensic indicators for CVE-2026-14677:
Check PostgreSQL version:
postgres --version or within psql: SELECT version();
Identify 32-bit build:
file $(which postgres) | grep 32-bit Returns "ELF 32-bit" if vulnerable architecture
List PL/Tcl and PL/Perl extensions:
SELECT lanname FROM pg_language WHERE lanname IN ('pltcl', 'plperl');
Check for suspicious function bodies (potential exploit indicators):
SELECT proname, prosrc FROM pg_proc
WHERE prolang IN (SELECT oid FROM pg_language WHERE lanname IN ('pltcl', 'plperl'))
AND length(prosrc) > 10000;
Monitor memory allocation errors in logs:
grep -i "memory" /var/log/postgresql/postgresql-.log grep -i "allocation" /var/log/postgresql/postgresql-.log
Audit function creation events:
SELECT FROM pg_stat_activity WHERE query LIKE '%CREATE FUNCTION%';
Exploit: (Educational Purposes!)
The following is for educational understanding only. Do not use against production systems.
Conceptual trigger (simplified):
-- A crafted PL/Perl function that could trigger wraparound CREATE OR REPLACE FUNCTION exploit_trigger() RETURNS void AS $$ In 32-bit Perl, large array indices can cause integer overflow my $size = 2147483648; 2³¹ + 1, wraps to small value my @large_array = (1) x $size; May undersize allocation return; $$ LANGUAGE plperl;
PL/Tcl variant:
CREATE OR REPLACE FUNCTION exploit_tcl() RETURNS void AS $$ Tcl's internal representation may overflow on 32-bit set size 2147483648 string repeat "A" $size $$ LANGUAGE pltcl;
Memory corruption observation (conceptual):
Monitor for segmentation faults or abnormal terminations dmesg | grep -i "postgres.segfault" journalctl -u postgresql | grep -i "fatal|core dumped"
Protection:
- Upgrade PostgreSQL to patched versions: 18.5, 17.11, 16.15, 15.19, or 14.24 (or later)
- Apply vendor patches from the official PostgreSQL repository
- Disable unused procedural languages if PL/Tcl or PL/Perl are not required:
DROP EXTENSION IF EXISTS plperl CASCADE; DROP EXTENSION IF EXISTS pltcl CASCADE;
- Restrict function creation privileges to trusted users only:
REVOKE CREATE ON SCHEMA public FROM PUBLIC;
- Use 64-bit builds where possible, as the wraparound is specific to 32-bit architectures
- Implement WAF or database firewall rules to detect anomalous function body submissions
- Enable detailed logging and monitor for out-of-bounds write attempts
Impact:
- Arbitrary Code Execution: Attackers can execute shell commands as the `postgres` OS user
- Data Breach: Full read access to all databases managed by the PostgreSQL instance (Confidentiality: HIGH)
- Data Manipulation: Insert, update, or delete any database records (Integrity: HIGH)
- Denial of Service: Crash the PostgreSQL server or corrupt system catalogs (Availability: HIGH)
- Lateral Movement: Compromised database server can be used to pivot to other internal systems
- Persistence: Malicious functions or triggers can be installed for long-term access
- Compliance Violations: Breaches may violate GDPR, HIPAA, PCI-DSS, and other regulatory frameworks
- Affected Versions: All PostgreSQL 32-bit builds before 18.5, 17.11, 16.15, 15.19, and 14.24 are vulnerable
- Similar Vulnerabilities: CVE-2026-6473 previously fixed similar integer wraparound issues
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Sources:
Reported By: nvd.nist.gov
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