CVE-2021-45958

Exp

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.

Published: 2022-01-01 Last update: 2024-11-21 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2021-45958 is rated Exploit Available (55.1/100): CVSS Medium severity, with medium exploitation likelihood (EPSS 0.29%). 3 public exploit reference(s) are indexed (Exploit-DB). Public exploits are available—assess exposure, apply mitigations, and prioritize patching.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Public exploit references (Exploit-DB) for CVE-2021-45958

EDB-ID Source Kind Published Link
— nvd_ref exploit_tag Exploit-DB ↗
— nvd_ref exploit_tag Exploit-DB ↗
— nvd_ref exploit_tag Exploit-DB ↗

Exploit prediction scoring system (EPSS) score for CVE-2021-45958

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2025-11-21 0.35% 0.29% -0.07%
2 2025-11-18 0.29% 0.35% +0.07%
3 2025-10-15 — 0.29% —

Full EPSS history (14 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2021-45958

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
5.5 3.1 MEDIUM
CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H Click to expand
Attack vector (AV:L)
They already need access on the box, or another person has to do something wrong; it’s not a remote drive-by.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:R)
A real person has to do something—click, install, enable—otherwise it doesn’t land.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 1.8 3.6 [email protected]
4.3 2.0 MEDIUM
AV:N/AC:M/Au:N/C:N/I:N/A:P Click to expand
Access vector (AV:N)
Can be exploited remotely over network reachability.
Access complexity (AC:M)
Exploitation needs some favorable conditions, but not exceptional ones.
Authentication (AU:N)
No authentication is required.
Confidentiality impact (C:N)
No confidentiality impact.
Integrity impact (I:N)
No integrity impact.
Availability impact (A:P)
Partial availability impact.
 8.6 2.9 [email protected]

Weakness enumeration for CVE-2021-45958

GitHub Security Advisory for CVE-2021-45958

GHSA-fh56-85cw-5pq6 · Severity: medium · Ecosystem: pip — UltraJSON vulnerable to Out-of-bounds Write

OS Trackers for CVE-2021-45958

vendor priority summary link
alpine medium CVE-2021-45958: 1 source package rows (py3-ujson); 8 state rows across 7 repos (3.17-community, 3.18-community, 3.19-community, 3.20-community, 3.21-community, 3.22-community, edge-community); fixed 8, open 0. https://security.alpinelinux.org/vuln/CVE-2021-45958
debian not yet assigned CVE-2021-45958 not yet assigned priority: Debian including 1 source packages (ujson), 5 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 4, open 1. https://security-tracker.debian.org/tracker/CVE-2021-45958
suse medium CVE-2021-45958 severity moderate: SUSE including 10 source package names (python-ujson, python2-ujson-1.35-150100.3.8.1, …), 26 product×package rows across 21 product lines (HPE Helion OpenStack 8, SUSE Linux Enterprise Module for Development Tools 15 SP4, … (21 product lines)): Fixed 21, Will Not Fix 5. https://www.suse.com/security/cve/CVE-2021-45958/
ubuntu medium CVE-2021-45958 medium priority: Ubuntu including 2 source packages (pandas, ujson), 30 status rows across 15 suites (bionic, focal, hirsute, impish, jammy, kinetic, lunar, mantic, noble, oracular, plucky, questing, trusty, upstream, xenial): ignored 11, needs-triage 7, not-affected 6, released 5, needed 1. https://ubuntu.com/security/CVE-2021-45958

Affected software / configurations for CVE-2021-45958

Vendor Product Version Raw CPE
ultrajson_project ultrajson < 5.2.0 cpe:2.3:a:ultrajson_project:ultrajson:*:*:*:*:*:python:*:*
debian debian_linux 9.0 cpe:2.3:o:debian:debian_linux:9.0:*:*:*:*:*:*:*
fedoraproject fedora 35 cpe:2.3:o:fedoraproject:fedora:35:*:*:*:*:*:*:*
fedoraproject fedora 36 cpe:2.3:o:fedoraproject:fedora:36:*:*:*:*:*:*:*
fedoraproject fedora 37 cpe:2.3:o:fedoraproject:fedora:37:*:*:*:*:*:*:*

References for CVE-2021-45958

URL Tags
https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=36009 Exploit Issue Tracking Third Party Advisory
https://github.com/google/oss-fuzz-vulns/blob/main/vulns/ujson/OSV-2021-955.yaml Exploit Third Party Advisory
https://github.com/ultrajson/ultrajson/issues/501 Exploit Issue Tracking Third Party Advisory
https://github.com/ultrajson/ultrajson/issues/502#issuecomment-1031747284 Issue Tracking Patch Third Party Advisory
https://github.com/ultrajson/ultrajson/pull/504 Patch Third Party Advisory
https://lists.debian.org/debian-lts-announce/2022/02/msg00023.html Mailing List Third Party Advisory
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/
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