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Vulnerability record · CVE-2021-45958 · published 1 January 2022

CVE-2021-45958: Ultrajson project ultrajson out-of-bounds write vulnerability

UUltrajson Project · Ultrajson

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.

5.5 CVSS 3.1 Medium EPSS 1.6% · top 25.9% CWE-787 · Out-of-bounds write
5.5CVSS 3.1 base score, v2 4.3
1.6%EPSS exploitation probability, 30 days
NoNot in CISA KEV
3Affected product versions listed by NVD
20References, 6 tagged exploit
17 Jun 2026Last modified by NVD

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.

CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H

Affected products

3 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=36009 ExploitIssue TrackingThird Party Advisory
https://github.com/google/oss-fuzz-vulns/blob/main/vulns/ujson/OSV-2021-955.yaml ExploitThird Party Advisory
https://github.com/ultrajson/ultrajson/issues/501 ExploitIssue TrackingThird Party Advisory
https://github.com/ultrajson/ultrajson/issues/502#issuecomment-1031747284 Issue TrackingPatchThird Party Advisory
https://github.com/ultrajson/ultrajson/pull/504 PatchThird Party Advisory
https://lists.debian.org/debian-lts-announce/2022/02/msg00023.html Mailing ListThird Party Advisory
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/CN7W3GOXALINKFUUE7ICQIC
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/NAU5N4A7EUK2AMUCOLYDD5A
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/O6JUWQTJLA2CMG4CJN7DCUV
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/ULX35TSWLBBIMEH44MUORPX
https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=36009 ExploitIssue TrackingThird Party Advisory
https://github.com/google/oss-fuzz-vulns/blob/main/vulns/ujson/OSV-2021-955.yaml ExploitThird Party Advisory
https://github.com/ultrajson/ultrajson/issues/501 ExploitIssue TrackingThird Party Advisory
https://github.com/ultrajson/ultrajson/issues/502#issuecomment-1031747284 Issue TrackingPatchThird Party Advisory
https://github.com/ultrajson/ultrajson/pull/504 PatchThird Party Advisory
https://lists.debian.org/debian-lts-announce/2022/02/msg00023.html Mailing ListThird Party Advisory
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/CN7W3GOXALINKFUUE7ICQIC
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/NAU5N4A7EUK2AMUCOLYDD5A
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/O6JUWQTJLA2CMG4CJN7DCUV
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/ULX35TSWLBBIMEH44MUORPX

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Source: NIST National Vulnerability Database (record CVE-2021-45958), CISA KEV, FIRST EPSS (scores of 2026-09-27). This page is refreshed as NVD updates the record.