What’s Vulnerable › Vulnerabilities

CVE-2021-45958

• Severity: medium (CVSS 5.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 1.7% probability of exploitation in the next 30 days
• Public exploit or detection template: yes
• Published: 2022-01-01 · updated 2026-06-17
• Weakness: CWE-787

Description

UltraJSON (aka ujson) through 5.1.0 has a stack-based buffer overflow in Buffer_AppendIndentUnchecked (called from encode). Exploitation can, for example, use a large amount of indentation.

Affected products

• Debian Linux: 9.0
• Fedoraproject Fedora: 35, 36, 37
• ultrajson: before 5.2.0 — fixed in 5.2.0

How to fix

Upgrade to a fixed version: ultrajson 5.2.0. Check the vendor advisory for mitigations.

References

• https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=36009
• https://github.com/google/oss-fuzz-vulns/blob/main/vulns/ujson/OSV-2021-955.yaml
• https://github.com/ultrajson/ultrajson/issues/501
• https://github.com/ultrajson/ultrajson/issues/502#issuecomment-1031747284
• https://github.com/ultrajson/ultrajson/pull/504
• https://lists.debian.org/debian-lts-announce/2022/02/msg00023.html
• https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/CN7W3GOXALINKFUUE7ICQIC2EF5HNKUQ/
• https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/NAU5N4A7EUK2AMUCOLYDD5ARXAJYZBD2/
• https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/O6JUWQTJLA2CMG4CJN7DCUVSOXLZIIXL/
• https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/ULX35TSWLBBIMEH44MUORPXYYRZKEDC6/
• https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=36009
• https://github.com/google/oss-fuzz-vulns/blob/main/vulns/ujson/OSV-2021-955.yaml

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