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Public proof of conceptFix available

CVE-2021-3177

A public proof of concept exists; no exploitation attested.

  • Published2021-01-19
  • WeaknessCWE-120

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

Description

Python 3.x through 3.9.1 has a buffer overflow in PyCArg_repr in _ctypes/callproc.c, which may lead to remote code execution in certain Python applications that accept floating-point numbers as untrusted input, as demonstrated by a 1e300 argument to c_double.from_param. This occurs because sprintf is used unsafely.

Timeline

dates in UTC
  1. 2021-01-1906:15CVE publishedNVD

Versions per branch

NVD · OSV
Python
BranchAffectedFixed in
3.6≥ 3.6.0, ≤ 3.6.12no fix published
3.7≥ 3.7.0, ≤ 3.7.9no fix published
3.8≥ 3.8.0, ≤ 3.8.7no fix published
3.9≥ 3.9.0, ≤ 3.9.1no fix published
python
BranchAffectedFixed in
3.9≥ 3.9.0, < 3.9.23.9.2
3.8≥ 3.8.0, < 3.8.83.8.8
3.7≥ 3.7.0, < 3.7.103.7.10
3.6< 3.6.133.6.13
libpython
BranchAffectedFixed in
3.9≥ 3.9.0, < 3.9.23.9.2
3.8≥ 3.8.0, < 3.8.83.8.8
3.7≥ 3.7.0, < 3.7.103.7.10
3.6< 3.6.133.6.13

10 more products in the sources.

as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.

Distribution builds and vendor advisories

Packages from OSV.dev and products from the vendors' CSAF advisories.

version not verifiedVersions not verified: read as OSV.dev and the vendors publish them, not checked against each vendor's release list.

Packages

  • babelRocky Linux:8all versions · fixed in 0:2.5.1-9.module+el8.4.0+403+9ae17a31
  • babelRocky Linux:8all versions · fixed in 0:2.7.0-10.module+el8.4.0+570+c2eaf144
  • babelRed Hat:enterprise_linux:8::appstreamall versions · fixed in 0:2.5.1-9.module+el8.1.0+3111+de3f2d8eand 1 other package
  • babelRed Hat:enterprise_linux:8::appstreamall versions · fixed in 0:2.7.0-10.module+el8.4.0+8888+89bc7e79and 1 other package
  • CythonRocky Linux:8all versions · fixed in 0:0.28.1-7.module+el8.4.0+403+9ae17a31
  • CythonRocky Linux:8all versions · fixed in 0:0.28.1-7.module+el8.5.0+706+735ec4b3
  • CythonRocky Linux:8all versions · fixed in 0:0.29.14-4.module+el8.4.0+570+c2eaf144
  • CythonRed Hat:enterprise_linux:8::appstreamall versions · fixed in 0:0.28.1-7.module+el8.1.0+3111+de3f2d8eand 3 other packages

344 more package ranges on OSV.dev

Vendor advisories

  • CVE-2021-3177 Red Hat Product Security819 products fixed · 17 known affected

    python: Stack-based buffer overflow in PyCArg_repr in _ctypes/callproc.c

    python.src as a component of Red Hat Enterprise Linux 5 · python as a component of Red Hat Enterprise Linux 6 · python-devel as a component of Red Hat Enterprise Linux 6 · +14 more

  • ICSA-23-348-10 CISA5 known affected

    Siemens SIMATIC S7-1500

    SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AB0) · SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AC0) · SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AB0) · +2 more

  • SSA-398330 Siemens ProductCERT5 known affected

    SSA-398330: Vulnerabilities in the additional GNU/Linux subsystem of the SIMATIC S7-1500 CPU 1518(F)-4 PN/DP MFP >= V3.1.0 and < V3.1.5

    SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AB0) >= V3.1.0 < V3.1.5 · SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AC0) >= V3.1.0 < V3.1.5 · SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AB0) >= V3.1.0 < V3.1.5 · +2 more

  • RHSA-2022:5235 Red Hat Product Security72 products fixed

    Red Hat Security Advisory: python security update

  • RHSA-2021:3252 Red Hat Product Security80 products fixed

    Red Hat Security Advisory: python27 security update

  • RHSA-2021:3254 Red Hat Product Security126 products fixed

    Red Hat Security Advisory: rh-python38 security, bug fix, and enhancement update

3 more advisories

Full record on NVD

Fix

  1. Vendor fix Siemens ProductCERT SSA-398330 · 1 productUpdate to V3.1.5 or later version
  2. Vendor fix CISA ICSA-23-348-10 · 5 productsUpdate to V3.1.5 or later version
  3. Vendor fix Red Hat Product Security RHSA-2022:5235 · 72 productsFor details on how to apply this update, which includes the changes described in this advisory, refer to: https://access.redhat.com/articles/11258
  4. Mitigation from the vendor CISA ICSA-23-348-10 · 5 productsOnly build and run applications from trusted sources.
  5. No fix available, says the vendor Red Hat Product Security CVE-2021-3177 · 1 productAffected
  6. No fix planned, says the vendor Red Hat Product Security CVE-2021-3177 · 16 productsOut of support scope

Advisories and patches

Detection

Nuclei template
none so far
ProjectDiscovery
Exploit-DB
no entry
Exploit-DB
Proof of concept
Metasploit modules
none listed
Metasploit Framework

Sources

Identifiers

Technical details

CVSS v3 Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Published
2021-01-19
Last Modified
2026-10-14
NVD status
Modified
GitHub Advisory
GHSA-hc96-xw56-vfwh

Frequently asked questions

What is CVE-2021-3177?

Python 3.x through 3.9.1 has a buffer overflow in PyCArg_repr in _ctypes/callproc.c, which may lead to remote code execution in certain Python applications that accept floating-point numbers as untrusted input, as demonstrated by a 1e300 argument to c_double.from_param. This occurs because sprintf is used unsafely.

Is CVE-2021-3177 actively exploited?

A proof-of-concept exploit exists for CVE-2021-3177, but active exploitation has not been confirmed at this time.

What is the CVSS score for CVE-2021-3177?

CVE-2021-3177 has a CVSS v3 base score of 9.8 (CRITICAL severity), with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.

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Sources for this record