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Fencer Vulns
high 7.5

CVE-2018-1000656 json

Flask is vulnerable to Denial of Service via incorrect encoding of JSON data

published 2018-08-20 8 y ago modified 2026-06-17 4 mo ago also GHSA-562c-5r94-xh97 , PYSEC-2018-66 , EUVD-2018-0075

cvss
7.5
version 3.0, NVD
cisa kev
Not listed
not in CISA's catalog
epss
3.9%
EPSS 3.9% chance of exploitation in 30 days, percentile 90%
public exploits
0
none known

Summary

The Pallets Project flask version Before 0.12.3 contains a CWE-20: Improper Input Validation vulnerability in flask that can result in Large amount of memory usage possibly leading to denial of service. This attack appear to be exploitable via Attacker provides JSON data in incorrect encoding. This vulnerability appears to have been fixed in 0.12.3. NOTE: this may overlap CVE-2019-1010083.

Patch / fix

  • pypi flask 0.12.3
  • palletsprojects flask 0.12.3
  • flask Debian 14, Debian 13, Debian 12 1.0.2-1

debian advisories DEBIAN-CVE-2018-1000656

  • flask Ubuntu 16.04 LTS 0.10.1-2ubuntu0.1
  • flask Ubuntu 18.04 LTS 0.12.2-3ubuntu0.1
  • flask Ubuntu Pro 14.04 LTS 0.10.1-2ubuntu0.1~esm1

ubuntu advisories UBUNTU-CVE-2018-1000656

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

  • python-flask RHEL 7 EXTRAS_OTHER 1:0.10.1-5.el7_7

red hat advisories RHSA-2020:0870

  • python-Flask SLE Module for Package Hub 15, SLE Module for Basesystem 15 0.12.4-3.3.26

suse advisories SUSE-SU-2019:0657-1

  • python-Flask openSUSE Leap 15.0 0.12.4-lp150.2.3.1

opensuse advisories openSUSE-SU-2019:1112-1

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-2018-1000656 updated cvss 7.5

python-flask: Denial of Service via crafted JSON file

  • Red Hat Ceph Storage 2 python-flask
    affected: no fix available
  • Red Hat Ceph Storage 3 python-flask Red Hat Storage 3 python-flask Red Hat Update Infrastructure 3 for Cloud Providers python-flask
    affected: no fix available “Fix deferred”
  • Red Hat Enterprise Linux 7 Extras python-flask 0.10.1-5.el7_7
    fixed: vendor fix RHSA-2020:0870
  • Red Hat Ceph Storage 7 python-flask Red Hat Enterprise Linux 8 python3-flask Red Hat Satellite 6 python-flask, python2-flask
    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

Exploit prediction

3.85% chance of exploitation in the next 30 days, higher than 90% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
NVD 3.0 7.5 CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
NVD 2.0 5.0 AV:N/AC:L/Au:N/C:N/I:N/A:P
GitHub 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Affected packages

ecosystem package affected fixed in
pypi flask
<0.12.3
0.12.3

Classification

Weakness
  • CWE-20 Improper Input Validation
Technology feeds

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.