CVE-2026-16554 — Integer Overflow Leading to Heap Buffer Overflow in cJSON
cJSON library is vulnerable to an integer overflow in the print_string_ptr() function in cJSON.c on 32-bit platforms. The escape_characters counter, a 32-bit size_t, can wrap around when processing strings containing approximately 858,993,460 or more control characters, causing the output buffer to be allocated based on an underestimated length. When cJSON_PrintBuffered() is used with a pre-allocated buffer, the subsequent write loop overflows the heap allocation. An attacker supplying a crafted JSON string to an application using cJSON on a 32-bit platform can cause a heap buffer overflow, potentially leading to remote code execution, information disclosure, or denial of service. Because project creator contact attempts were unsuccessful, the vulnerability has only been confirmed in version 1.7.19 but may also affect other versions.
Who exploits it and how urgent it is
A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.
How the score was calculated
- Technical severity (high)+6
The score orders the patch queue; it does not replace your asset context (internet exposure, criticality, compensating controls).
Triage
Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.
CISA SSVC assessment CISA
Three decision points CISA publishes for the CVEs it assesses (SSVC 2.0.3). A stakeholder decision, not a severity score.
Remediation
Fixes and mitigations documented by the sources — linked to the original advisory.
No fix documented by the sources we poll. That does not mean none exists: check the vendor advisory.
First 24 hours
Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.
- Identify exposed assets running the affected vendor/product/version combinations (Davegamble Cjson).
- No fix documented in the sources: reduce exposure and monitor the vendor advisory.
- Search available logs for exploit probes matching the vulnerability class (memory corruption), errors and authentication anomalies.
Affected scope
Vendor, product and versions as the sources word them.
| Vendor | Product | Versions | Status | Source |
|---|---|---|---|---|
| Davegamble | Cjson | version 1.7.19 | Vulnerable | NIST National Vulnerability Database |
| Davegamble | Cjson | version 1.7.19 | Vulnerable | CVE Program (cve.org) e CISA ADP |
Attack characteristics
The CVSS vector, decoded. It describes the attack, not your exposure to it.
Every base score collected
Sources score independently and may disagree; each row says who scored it and under which version.
| Score | Version | Severity | Expl. | Impact | Scored by |
|---|---|---|---|---|---|
| 5.1 | CVSS 4.0 | Medium | — | — | cvd@cert.pl via NIST National Vulnerability Database |
| 5.1 | CVSS 4.0 | Medium | — | — | CERT-PL via CVE Program (cve.org) e CISA ADP |
| 7.8 | CVSS 3.1 | High | 1.8 | 5.9 | nvd@nist.gov via NIST National Vulnerability Database |
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H (score shown at the top: nvd@nist.gov) Weakness MITRE
Weakness class according to MITRE’s CWE catalog.
Detection
Read off the CVSS vector and the weakness class. Starting points, not tested rules.
- Local/physical vector: focus on endpoint telemetry (EDR) from affected hosts.
- Correlate service crashes/restarts with inbound traffic; repeated crashes may indicate attempts.
Timeline
What happened to this CVE, newest first.
- 2026
- Affected products added · davegamble/cjson
- SSVC assessment updated
- Record published
- CVSS changed · 7.8
- Source status changed · → Analyzed
- Record created in this database
- CVE published
Source activity
Repeated readings are counted rather than listed.
- 1× Official description updated · Oct 15, 2026 – Oct 15, 2026
References
4 on the record
Elsewhere on this site
Related CVEs (same products)
- High CVE-2026-29036 cJSON 1.7.19 Wrong-Key Modification via JSON Pointer Escape Decoding Aug 11, 2026
- High CVE-2026-67215 cJSON JSON Patch copy/add Uncontrolled Recursion Stack Exhaustion Jul 29, 2026
- High CVE-2026-67216 cJSON cJSON_Compare Exponential Complexity Denial of Service Jul 29, 2026
- Medium CVE-2026-67217 cJSON through 1.7.19 applies RFC 6902 JSON Patch operations non-atomically in… Jul 29, 2026
Not in any source we poll
Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.
- No FIRST EPSS score.
- No fixed version, patch or mitigation documented.
- No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
- No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
- No exploit packet captures, log samples, or incident case IDs supplied.
Answered from this record
Text assembled only from the fields above — no additional claims.
What should defenders know first?
CVE-2026-16554 is "Integer Overflow Leading to Heap Buffer Overflow in cJSON", rated High. It affects Cjson (Davegamble); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. CVSS 7.8 describes technical severity. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.
Comments
Moderated technical discussion. Read the community guidelines.
No comments yet.
Sign in or create an account to comment and suggest corrections.