Integer Overflow Leading to Heap Buffer Overflow in cJSON

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-16554
StatePUBLISHED
AssignerCERT-PL
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-07-27 09:16:37 UTC
Updated2026-07-31 14:16:47 UTC
DescriptioncJSON 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.

Risk And Classification

Primary CVSS: v4.0 5.1 MEDIUM from [email protected]

CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:L/SI:L/SA:L/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

EPSS: 0.002950000 probability, percentile 0.217770000 (date 2026-08-01)

Problem Types: CWE-190 | CWE-190 CWE-190 Integer overflow or wraparound

VersionSourceTypeScoreSeverityVector
4.0[email protected]Secondary5.1MEDIUMCVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:L/SI:L/SA:L/E:X/C...
4.0CNACVSS5.1MEDIUMCVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:L/SI:L/SA:L

CVSS v4.0 Breakdown

Attack Vector
Local
Attack Complexity
Low
Attack Requirements
None
Privileges Required
None
User Interaction
None
Confidentiality
None
Integrity
None
Availability
Low
Sub Conf.
Low
Sub Integrity
Low
Sub Availability
Low

CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:L/SI:L/SA:L/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA DaveGamble CJSON affected 1.7.19 semver Not specified

References

ReferenceSourceLinkTags
www.openwall.com/lists/oss-security/2026/07/31/4 af854a3a-2127-422b-91ae-364da2661108 www.openwall.com
www.openwall.com/lists/oss-security/2026/07/30/26 af854a3a-2127-422b-91ae-364da2661108 www.openwall.com
github.com/DaveGamble/cJSON [email protected] github.com
cert.pl/en/posts/2026/07/CVE-2026-16554 [email protected] cert.pl
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis

Vendor Comments And Credit

Discovery Credit

CNA: Michał Majchrowicz (AFINE Team) (en)

CNA: Marcin Wyczechowski (AFINE Team) (en)

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