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Fencer Vulns
high 7.8

CVE-2020-12762 json

json-c through 0.14 has an integer overflow and out-of-bounds write via a large JSON file, as demonstrated by printbuf_memappend.

published 2020-05-09 6 y ago modified 2026-10-14 26 d ago also EUVD-2020-5047

cvss
7.8
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
1.9%
EPSS 1.9% chance of exploitation in 30 days, percentile 79%
public exploits
0
none known

Summary

json-c through 0.14 has an integer overflow and out-of-bounds write via a large JSON file, as demonstrated by printbuf_memappend.

Patch / fix

  • Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP V3.1.5
  • Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP V3.1.5
  • Siemens SIMATIC S7-1500 TM MFP - GNU/Linux subsystem V1.1
  • Siemens SIPLUS S7-1500 CPU 1518-4 PN/DP MFP V3.1.5
  • Siemens RUGGEDCOM ROX MX5000 V2.17.0
  • Siemens RUGGEDCOM ROX MX5000RE V2.17.0
  • Siemens RUGGEDCOM ROX RX1400 V2.17.0
  • Siemens RUGGEDCOM ROX RX1500 V2.17.0
  • Siemens RUGGEDCOM ROX RX1501 V2.17.0
  • Siemens RUGGEDCOM ROX RX1510 V2.17.0
  • Siemens RUGGEDCOM ROX RX1511 V2.17.0
  • Siemens RUGGEDCOM ROX RX1512 V2.17.0
  • Siemens RUGGEDCOM ROX RX1524 V2.17.0
  • Siemens RUGGEDCOM ROX RX1536 V2.17.0
  • Siemens RUGGEDCOM ROX RX5000 V2.17.0
  • json-c Debian 14, Debian 13, Debian 12 0.13.1+dfsg-8
  • libfastjson Debian 14, Debian 13, Debian 12 1.2304.0-1

debian advisories DEBIAN-CVE-2020-12762

  • json-c Ubuntu 16.04 LTS 0.11-4ubuntu2.6
  • json-c Ubuntu 18.04 LTS 0.12.1-1.3ubuntu0.3
  • json-c Ubuntu 20.04 LTS 0.13.1+dfsg-7ubuntu0.3
  • json-c Ubuntu Pro 14.04 LTS 0.11-3ubuntu1.2+esm3

ubuntu advisories UBUNTU-CVE-2020-12762

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • libfastjson RHEL 8 0.99.9-2.el8
  • libfastjson RHEL 9 0.99.9-5.el9
  • json-c RHEL 8 0.13.1-2.el8
  • libfastjson RHEL 9.0 EUS 0.99.9-3.el9_0.1
  • libfastjson RHEL 9.2 EUS 0.99.9-3.el9_2.1
  • libfastjson RHEL 8.8 EUS 0.99.9-1.el8_8.1
  • libfastjson RHEL 8.6 EUS 0.99.9-1.el8_6.1

red hat advisories RHSA-2024:1154RHSA-2024:1086RHSA-2024:0573RHSA-2024:0411RHSA-2023:6976RHSA-2023:6431

  • libfastjson SLES for SAP 12 SP5, SLES 12 SP5 0.99.8-3.6.1
  • libfastjson SLES for SAP 15 SP3, SLES for SAP 15 SP2, SLES 15 SP3-LTSS +4 more 0.99.8-150000.3.3.1
  • libfastjson SLE Module for Basesystem 15 SP4, openSUSE Leap 15.4 0.99.9-150400.3.3.1
  • json-c SLES for SAP 12 SP5, SLES for SAP 12 SP4, SLES 12 SP5 +6 more 0.12.1-4.3.1
  • json-c SLES 15 SP2-BCL, SLES 15 SP1-BCL, SLE Real Time 15 SP2 +20 more 0.13-3.3.1

suse advisories SUSE-SU-2024:1846-1SUSE-SU-2024:1775-1SUSE-SU-2023:2135-1SUSE-SU-2022:3001-1SUSE-SU-2022:0184-2SUSE-SU-2022:0184-1

  • json-c openSUSE Leap 15.3 0.13-3.3.1

opensuse advisories openSUSE-SU-2022:0184-1

  • libfastjson AlmaLinux 8 0.99.9-2.el8
  • libfastjson AlmaLinux 9 0.99.9-5.el9

almalinux advisories ALSA-2023:6976ALSA-2023:6431

  • libfastjson Rocky Linux 8 0.99.9-2.el8
  • libfastjson Rocky Linux 9 0.99.9-5.el9
  • json-c Rocky Linux 8 0.13.1-2.el8

rocky linux advisories RLSA-2023:6976RLSA-2023:6431RLSA-2021:4382

  • json-c Alpine 3.11, Alpine 3.10, Alpine 3.9 0.13.1-r1
  • json-c Alpine 3.24, Alpine 3.23, Alpine 3.22 +10 more 0.14-r1
  • libfastjson Alpine 3.24, Alpine 3.23, Alpine 3.22 +7 more 1.2304.0-r0

alpine advisories ALPINE-CVE-2020-12762

Alpine secdb © Alpine Linux, from https://secdb.alpinelinux.org via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • json-c CBL-Mariner 2.0 0.15-2

azure linux advisories AZL-6506

Azure Linux vulnerability data, Copyright (c) Microsoft Corporation, from https://github.com/microsoft/AzureLinuxVulnerabilityData via OSV, under the MIT licence; changed: normalised to fixed package versions per release. MIT

  • json-c Arch Linux 0.15-1

arch linux advisories AVG-1160

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2020-12762 updated cvss 7.8

libfastjson: integer overflow and out-of-bounds write via a large JSON file

  • Red Hat Enterprise Linux 6 json-c Red Hat Enterprise Linux 7 json-c
    affected: workaround, no fix planned “Will not fix”
  • Red Hat CodeReady Linux Builder (v. 8) json-c-doc 0.13.1-2.el8
    fixed: vendor fix RHSA-2021:4382
  • Red Hat CodeReady Linux Builder (v. 9) libfastjson-devel 0.99.9-5.el9, libfastjson-debuginfo 0.99.9-5.el9, libfastjson-debugsource 0.99.9-5.el9
    fixed: vendor fix RHSA-2023:6431
  • Red Hat Enterprise Linux AppStream (v. 8) libfastjson 0.99.9-2.el8
    fixed: vendor fix RHSA-2021:4382
  • Red Hat Enterprise Linux AppStream (v. 9) libfastjson 0.99.9-5.el9
    fixed: vendor fix RHSA-2023:6431
  • Red Hat Enterprise Linux AppStream EUS (v.8.6) libfastjson 0.99.9-1.el8_6.1
    fixed: vendor fix RHSA-2024:0411
  • Red Hat Enterprise Linux AppStream EUS (v.8.8) libfastjson 0.99.9-1.el8_8.1
    fixed: vendor fix RHSA-2024:0573
  • Red Hat Enterprise Linux AppStream EUS (v.9.0) libfastjson 0.99.9-3.el9_0.1
    fixed: vendor fix RHSA-2024:1154
show 3 more
  • Red Hat Enterprise Linux AppStream EUS (v.9.2) libfastjson 0.99.9-3.el9_2.1
    fixed: vendor fix RHSA-2024:1086
  • Red Hat Enterprise Linux BaseOS (v. 8) json-c 0.13.1-2.el8
    fixed: vendor fix RHSA-2021:4382
  • Red Hat Enterprise Linux 9 json-c
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

cisa ICSA-23-348-10 updated cvss 7.8

Siemens SIMATIC S7-1500

  • Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AB0) >= 3.1.0, < 3.1.5 Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AC0) >= 3.1.0, < 3.1.5 Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AB0) >= 3.1.0, < 3.1.5 Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AC0) >= 3.1.0, < 3.1.5 Siemens SIPLUS S7-1500 CPU 1518-4 PN/DP MFP (6AG1518-4AX00-4AC0) >= 3.1.0, < 3.1.5
    affected: fixed in V3.1.5, mitigation support.industry.siemens.com

Facts from CISA's republication of the vendor's own advisory (CSAF); the linked advisory is the authoritative source. CISA notification · csaf

cisa ICSA-23-166-11 updated cvss 7.8

Siemens SIMATIC S7-1500 TM MFP Linux Kernel

Facts from CISA's republication of the vendor's own advisory (CSAF); the linked advisory is the authoritative source. CISA notification · csaf

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
total
Assessed
17 mo ago

Exploit prediction

1.90% chance of exploitation in the next 30 days, higher than 79% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • github.com https://github.com/json-c/json-c/pull/592 referenced PoC, tagged "exploit" by a source, unverified
  • github.com https://github.com/rsyslog/libfastjson/issues/161 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CISA ADP 3.1 7.8 CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
NVD 3.1 7.8 CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
CNA 3.1 7.8 CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
NVD 2.0 6.8 AV:N/AC:M/Au:N/C:P/I:P/A:P

Affected products

  • Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP
  • Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP
  • Siemens SIMATIC S7-1500 TM MFP - GNU/Linux subsystem
  • Siemens SIPLUS S7-1500 CPU 1518-4 PN/DP MFP
  • Siemens RUGGEDCOM ROX MX5000
  • Siemens RUGGEDCOM ROX MX5000RE
  • Siemens RUGGEDCOM ROX RX1400
  • Siemens RUGGEDCOM ROX RX1500
  • Siemens RUGGEDCOM ROX RX1501
  • Siemens RUGGEDCOM ROX RX1510
  • Siemens RUGGEDCOM ROX RX1511
  • Siemens RUGGEDCOM ROX RX1512
  • Siemens RUGGEDCOM ROX RX1524
  • Siemens RUGGEDCOM ROX RX1536
  • Siemens RUGGEDCOM ROX RX5000

Classification

Weakness

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.