How severe is CVE-2026-54903?

CVE-2026-54903 has a CVSS 4.0 base score of 6.3, rated medium severity.

Is CVE-2026-54903 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (17th percentile), an estimate of the probability of exploitation in the next 30 days.

How do I fix CVE-2026-54903?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

When was CVE-2026-54903 published?

CVE-2026-54903 was published on 2026-07-01.

CVE-2026-54903

CVE-2026-54903 is a medium-severity vulnerability with a CVSS 4.0 base score of 6.3. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-190.

Key facts

Severity: Medium (CVSS 4.0 base score 6.3)
EPSS exploit prediction: 0% (17th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-190
Published: 2026-07-01
Last modified: 2026-07-01

Description

Oj (Optimized JSON) is a JSON parser and Object marshaller packaged as a Ruby gem. In versions prior to 3.17.2, Oj.load is vulnerable to heap corruption when parsing a JSON string longer than 2 GB. An integer overflow in buf_append_string (buf.h:61) converts the string length to a large negative size_t, causing memcpy to copy an astronomically large amount of data out of bounds. This crashes the process and can corrupt adjacent heap memory. The issue has been fixed in version 3.17.2.

Frequently asked questions

What is CVE-2026-54903?: Oj (Optimized JSON) is a JSON parser and Object marshaller packaged as a Ruby gem. In versions prior to 3.17.2, Oj.load is vulnerable to heap corruption when parsing a JSON string longer than 2 GB. An integer overflow in buf_append_string (buf.h:61) converts the string length to a large negative size_t, causing memcpy to copy an astronomically large amount of data out of bounds. This crashes the process and can corrupt adjacent heap memory. The issue has been fixed in version 3.17.2.
How severe is CVE-2026-54903?: CVE-2026-54903 has a CVSS 4.0 base score of 6.3, rated medium severity.
Is CVE-2026-54903 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (17th percentile), an estimate of the probability of exploitation in the next 30 days.
How do I fix CVE-2026-54903?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2026-54903 published?: CVE-2026-54903 was published on 2026-07-01.

References

https://github.com/ohler55/oj/security/advisories/GHSA-475m-ph3x-64gp

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