cJSON Library Integer Overflow Flaw Disclosed
A heap buffer overflow in the cJSON library's print_string_ptr() function on 32-bit platforms could enable RCE, info disclosure, or DoS.
Sourcecert.pl — open the original
What to check
- Applies to
- The 1 CVE named below. Whether you run an affected version is not assessed: check the versions the source lists.
- Exploitation
- No exploitation in the wild and no public exploit is recorded for the CVEs named.
CERT Polska coordinated disclosure of CVE-2026-16554, an integer overflow vulnerability in the widely-used DaveGamble cJSON library. The flaw resides in the print_string_ptr() function, where a 32-bit size_t counter tracking escape characters can wrap around when processing strings containing roughly 858,993,460 or more control characters. This causes the output buffer to be allocated based on an underestimated length, and when cJSON_PrintBuffered() is used with a pre-allocated buffer, the subsequent write loop overflows the heap allocation.
An attacker able to supply a crafted JSON string to an application using cJSON on a 32-bit platform could trigger a heap buffer overflow, potentially leading to remote code execution, information disclosure, or denial of service. The vulnerability has only been confirmed in version 1.7.19, though other versions may be affected as well. Notably, vendor contact attempts by CERT Polska were unsuccessful, meaning no official patch has been coordinated or confirmed at time of disclosure, leaving affected 32-bit deployments potentially exposed.
The vulnerability was reported by Michał Majchrowicz and Marcin Wyczechowski of AFINE Team through CERT Polska's coordinated vulnerability disclosure process. No active exploitation has been reported; this is a proactive disclosure of a library-level flaw requiring specific conditions (32-bit platform, large control-character input, use of cJSON_PrintBuffered) to trigger.
Mentioned in this report
Source reporting: https://cert.pl/en/posts/2026/07/CVE-2026-16554
Free public brief. Slack alerts on the vendors you run come with the paid plans, and a new account gets three days of them, no card.
What this brief leaves out
This page is the free tier: the write-up, the severity, the names. In the app the same report carries live profiles of the CVEs it names. The paid plans add the security research and news reporting the free tier leaves out.
It sits in a corpus of 16,433 reports from 149 sources, 661 of them written in the last seven days, and it grows through the day.
A new account starts with three days of all of it, no card, then keeps the government and CERT reporting free. Slack alerts are a paid-plan feature: name the vendors you run and Slack hears about the reports that touch them, not the rest of the week's. Nothing is charged unless you subscribe.
Create a free account What it costs