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CVE-2026-17543 is a high-severity SQL injection vulnerability residing in PHP’s PostgreSQL extension (ext-pgsql). The flaw stems from improper escaping of backslash characters within attacker-controlled parameters, allowing for trivial SQL injection across PHP versions 8.2. before 8.2.33, 8.3. before 8.3.33, 8.4. before 8.4.24, and 8.5. before 8.5.9.
The root cause lies deep within the PHP runtime itself, specifically in the internal `php_pgsql_convert()` function—the backbone for convenience functions like pg_select(), pg_insert(), pg_update(), and pg_delete(). This function uses `PQescapeStringConn()` from libpq to sanitize user-supplied values, then wraps the result in PostgreSQL escape string constants using the `E’…’` format via php_pgsql_add_quotes().
The vulnerability manifests when PostgreSQL operates with standard_conforming_strings = on—the default setting since PostgreSQL 9.1. In this mode, `PQescapeStringConn()` does not escape backslash characters, as backslashes are no longer treated as escape characters in standard SQL strings. However, because PHP wraps the escaped value inside `E’…’` (an escape string constant), the context changes: within E'...', backslashes are interpreted as escape characters.
An attacker can supply a malicious payload such as zzz' OR 1=1 --. When processed, the backslash escapes the closing single quote delimiter, breaking out of the string context entirely. The closing quote is absorbed as part of the escape sequence, and the attacker’s SQL code becomes part of the query. The fix involves switching from `E’…’` escape string constants to standard non-escaping string constants.
This vulnerability is remotely exploitable without authentication, requires no user interaction, and is automatable. With a CVSS 4.0 base score of 8.1 (HIGH), it poses critical risks to confidentiality, integrity, and availability. Any PHP application passing attacker-controlled input through the affected `pg_()` functions against a PostgreSQL backend is vulnerable—which, given PostgreSQL’s default settings, represents the vast majority of deployments.
DailyCVE Form:
Platform: PHP (ext-pgsql)
Version: 8.2<8.2.33/8.3<8.3.33/8.4<8.4.24/8.5<8.5.9
Vulnerability: SQL Injection (CWE-89)
Severity: HIGH (CVSS 4.0: 8.1)
date: 2026-07-30
Prediction: 2026-08-03 (patches released)
What Undercode Say:
Check PHP version php -v Check if ext-pgsql is loaded php -m | grep pgsql Check PostgreSQL standard_conforming_strings setting psql -c "SHOW standard_conforming_strings;" Exploit payload example curl "http://target.com/page.php?id=zzz%27%20OR%201=1%20--" pg_query() vulnerable example (conceptual) $result = pg_query($conn, "SELECT FROM users WHERE name = E'$input'"); Input: zzz' OR 1=1 -- Becomes: SELECT FROM users WHERE name = E'zzz' OR 1=1 --' Affected functions pg_select() | pg_insert() | pg_update() | pg_delete()
Exploit:
An attacker crafts input containing a backslash followed by a single quote and additional SQL commands. For example, submitting `zzz\’ OR 1=1 –` through a web form that uses `pg_insert()` or `pg_select()` with unsanitized user input. When PHP wraps this in E'...', the backslash escapes the closing quote, breaking out of the string. The resulting query executes the attacker’s injected SQL, enabling data extraction, modification, or deletion.
Protection:
- Immediate: Upgrade to PHP 8.2.33, 8.3.33, 8.4.24, or 8.5.9 (or later).
- If patching is delayed: Audit all code using
pg_select(),pg_insert(),pg_update(), andpg_delete(); replace with parameterized queries or prepared statements. - Compensating: Implement strict input validation and Web Application Firewall (WAF) rules.
- PostgreSQL: Temporarily set `standard_conforming_strings = off` (not recommended for production).
Impact:
- Confidentiality: Attackers can read arbitrary data from the connected PostgreSQL database.
- Integrity: Attackers can modify or insert malicious data.
- Availability: Attackers can delete data or issue destructive commands.
- Scope: Widespread exposure across the PHP ecosystem due to PHP’s popularity and PostgreSQL’s default settings.
- Risk: Complete system compromise when combined with other attack vectors.
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Sources:
Reported By: nvd.nist.gov
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