CVE-2026-54133

jmespath.php has CompilerRuntime code injection via unescaped function names

Workarounds

If you cannot upgrade immediately, disable JP_PHP_COMPILE and do not use JmesPath\CompilerRuntime with attacker-controlled expressions. Use the default AstRuntime for untrusted expressions. Applications that must continue accepting untrusted JMESPath expressions before upgrading should ensure those expressions are never evaluated by the compiler runtime.

mtdowling/jmespath.php can generate and execute attacker-controlled PHP code when JmesPath\CompilerRuntime is used with an attacker-controlled JMESPath expression. The compiler emits parsed JMESPath function names into generated PHP source without sufficient escaping. A crafted expression can cause the generated cache file to contain executable attacker-controlled PHP, which is then loaded by the compiler runtime.

A vulnerable flow is:

1. An application accepts or constructs a JMESPath expression using attacker-controlled input.
2. The expression is evaluated with JmesPath\CompilerRuntime, or with JmesPath\search() while JP_PHP_COMPILE is enabled.
3. The crafted expression uses a non-identifier value where the parser accepts a function callee.
4. The compiler writes that value into generated PHP source without safely escaping it as a PHP string literal.
5. The generated source is written to the compiled-expression cache directory.
6. CompilerRuntime loads the generated cache file.
7. The injected PHP executes in the context of the affected application.

In that flow, an attacker can execute arbitrary PHP code with the privileges of the PHP process. The searched data document is not sufficient to exploit this issue by itself; the attacker must be able to influence the JMESPath expression string.

The default runtime used by JmesPath\search() is AstRuntime, which interprets the parsed expression tree and is not affected unless JP_PHP_COMPILE is enabled. Applications are most likely to be affected when they explicitly instantiate JmesPath\CompilerRuntime, enable JP_PHP_COMPILE as a performance optimization, and allow users to provide JMESPath expressions for filtering, querying, or transforming data.

The application does not adequately validate input before processing it, allowing unexpected values to reach sensitive code paths. Typical impact: varies by context: data corruption, logic bypass, or denial of service.

CVE-2026-54133 has a CVSS score of 9.8 (Critical). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (2.9.1); upgrading removes the vulnerable code path.

Kodem intelligence

Already deployed Kodem?

The issue is patched in 2.9.1 and later.

1. What is CVE-2026-54133? CVE-2026-54133 is a critical-severity improper input validation vulnerability in mtdowling/jmespath.php (composer), affecting versions < 2.9.1. It is fixed in 2.9.1. The application does not adequately validate input before processing it, allowing unexpected values to reach sensitive code paths.
2. How severe is CVE-2026-54133? CVE-2026-54133 has a CVSS score of 9.8 (Critical). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of mtdowling/jmespath.php are affected by CVE-2026-54133? mtdowling/jmespath.php (composer) versions < 2.9.1 is affected.
4. Is there a fix for CVE-2026-54133? Yes. CVE-2026-54133 is fixed in 2.9.1. Upgrade to this version or later.
5. Is CVE-2026-54133 exploitable, and should I be worried? Whether CVE-2026-54133 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2026-54133 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2026-54133? Upgrade mtdowling/jmespath.php to 2.9.1 or later.