CVE-2026-16554: cJSON library is vulnerable to an integer overflow in the print_string_ptr() function in cJSON.c on 32-bit pla

Routine

HIGH 7.8DOWNGRADE

CVE-2026-16554 is a high-severity flaw (CVSS 7.8) affecting cjson. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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 th

Why this priority

High severity

A fixed release or distro patch exists.

Risk facts

CVSS score	7.8 (High)
Attack vector	Local
Attack complexity	Low
Privileges needed	Low
User interaction	None
EPSS exploit chance	0.3% (top 79%)
CISA exploited list	No
Weakness	CWE-190
Published	2026-07-27
Last modified	2026-10-24

Publisher (CNA): CERT.PL · Vendor: davegamble

Last updated 2026-10-24 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-07-27 09:16 UTCPublished CVE record published
2026-10-24 13:10 UTCUpdated Record last modified

davegamble cjson DOWNGRADE

Affected: 1.7.19

Fixed in: no fixed release known

Safe to downgrade to: a release before 1.7.19

1. Check installed version

apt-cache policy cjson || rpm -q cjson || cjson --version

2. No fixed release: DOWNGRADE to a release before 1.7.19 (Debian / Ubuntu)

apt-cache madison cjson sudo apt install cjson=<VERSION_BEFORE_1.7.19> sudo apt-mark hold cjson

2. No fixed release: DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list cjson sudo dnf downgrade cjson-<VERSION_BEFORE_1.7.19> sudo dnf versionlock add cjson

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

Exact fixes by distribution

A distro patch exists: prefer upgrading over downgrading.

Fedora 46 · sugar-clock · FIXED · 22.1-17.fc46 · FEDORA-2026-57948849df · source

sudo dnf upgrade --advisory=FEDORA-2026-57948849df

Fedora ELN · selinux-policy · FIXED · 45.23-1.eln159 · FEDORA-2026-3668c969a2 · source

sudo dnf upgrade --advisory=FEDORA-2026-3668c969a2

Ubuntu 20.04 · cjson · DEFERRED

Ubuntu 22.04 · cjson · DEFERRED

Ubuntu 24.04 · cjson · DEFERRED

Debian 12 · cjson · NO FIX YET

Debian 13 · cjson · NO FIX YET

RHEL 8 · rpm-ostree · NOT AFFECTED

Advisories and coverage

Official advisories

CERT Polska: Vulnerability in DaveGamble cJSON library 2026-07-27

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-16554?

cjson: downgrade or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2026-16554 being exploited?

CVE-2026-16554 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-16554 affect?

CVE-2026-16554 affects cjson. Severity is high (CVSS 7.8). 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 858,993,4

How urgent is CVE-2026-16554?

Priority 32/100. High severity

Related CVEs

CVE-2026-67215 HIGH 7.5 UPGRADE cJSON through 1.7.19 is vulnerable to uncontrolled recursion leading to stack exhaustion when an untrusted RFC
CVE-2026-67216 MEDIUM 5.9 UPGRADE cJSON through 1.7.19 contains an inefficient algorithmic complexity flaw in cJSON_Compare()
CVE-2026-67217 MEDIUM 5.3 UPGRADE cJSON through 1.7.19 applies RFC 6902 JSON Patch operations non-atomically in apply_patch() in cJSON_Utils.c

References

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