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Fencer Vulns
high 7.5

CVE-2021-21240 json

Regular Expression Denial of Service in httplib2

published 2021-02-08 5 y ago modified 2026-09-10 1 mo ago also GHSA-93xj-8mrv-444m , PYSEC-2021-16 , EUVD-2021-0098

cvss
7.5
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
3.7%
EPSS 3.7% chance of exploitation in 30 days, percentile 89%
public exploits
0
none known

Summary

httplib2 is a comprehensive HTTP client library for Python. In httplib2 before version 0.19.0, a malicious server which responds with long series of "\xa0" characters in the "www-authenticate" header may cause Denial of Service (CPU burn while parsing header) of the httplib2 client accessing said server. This is fixed in version 0.19.0 which contains a new implementation of auth headers parsing using the pyparsing library.

Patch / fix

  • pypi httplib2 0.19.0
  • httplib2_project httplib2 0.19.0
  • python-httplib2 Debian 14, Debian 13, Debian 12 0.20.2-1

debian advisories DEBIAN-CVE-2021-21240

  • python-httplib2 openstack 16.1 0.13.1-2.el8ost
  • python3-httplib2 openstack 16.1 0.13.1-2.el8ost

red hat advisories RHSA-2021:2116

  • python-httplib2 OpenStack Cloud Crowbar 8, OpenStack Cloud 8, HPE Helion OpenStack 8 0.19.0-7.3.1
  • python-httplib2 SLE Module for Public Cloud 12, OpenStack Cloud 7 0.19.0-7.7.1
  • python-httplib2 SLE Module for Package Hub 15 SP3, SLE Module for Package Hub 15 SP2, SLE Module for Basesystem 15 SP3 +1 more 0.19.0-3.3.1
  • python-httplib2 OpenStack Cloud Crowbar 9, OpenStack Cloud 9 0.19.0-8.3.4
  • python-httplib2 SLE Module for Public Cloud 15 0.19.0-1.8.1

suse advisories SUSE-SU-2021:1808-1SUSE-SU-2021:1807-1SUSE-SU-2021:1806-1SUSE-SU-2021:1779-1SUSE-SU-2021:1637-1

  • python-httplib2 openSUSE Tumbleweed 0.32.0-1.1
  • python-httplib2 openSUSE Tumbleweed 0.22.0-4.5
  • python-httplib2 openSUSE Tumbleweed 0.19.1-1.2
  • python-httplib2 openSUSE Leap 15.3 0.19.0-3.3.1
  • python-httplib2 Package Hub 15 SP2 0.19.0-bp152.3.3.1
  • python-httplib2 openSUSE Leap 15.2 0.19.0-lp152.6.3.1

opensuse advisories openSUSE-SU-2026:11203-1openSUSE-SU-2024:14141-1openSUSE-SU-2024:11231-1openSUSE-SU-2021:1806-1openSUSE-SU-2021:0796-1openSUSE-SU-2021:0772-1

  • py3-httplib2 Alpine 3.24, Alpine 3.23, Alpine 3.22 +8 more 0.19.0-r0

alpine advisories ALPINE-CVE-2021-21240

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

  • python-httplib2 Arch Linux 0.19.0-1

arch linux advisories AVG-1546

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-2021-21240 updated cvss 7.5

python-httplib2: Regular expression denial of service via malicious header

  • Red Hat Ceph Storage 2 python-httplib2 Red Hat Enterprise Linux 7 fence-agents, fence-agents-all, fence-agents-apc, fence-agents-aws, fence-agents-eps, fence-agents-gce, +38 more
    affected: workaround, no fix planned “Out of support scope”
  • Red Hat Enterprise Linux 8 python3-httplib2
    affected: workaround, no fix available “Fix deferred”
  • Red Hat OpenStack Platform 10 (Newton) python-httplib2
    affected: workaround, no fix planned “Out of support scope”
  • Red Hat OpenStack Platform 13 (Queens) python-httplib2
    affected: workaround, no fix planned “Will not fix”
  • Red Hat Storage 3 python-httplib2 Red Hat Update Infrastructure 3 for Cloud Providers python-httplib2
    affected: workaround, no fix available “Fix deferred”
  • Red Hat OpenStack Platform 16.1 python-httplib2 0.13.1-2.el8ost, python3-httplib2 0.13.1-2.el8ost
    fixed: vendor fix RHSA-2021:2116
  • Red Hat Enterprise Linux 9 python-httplib2
    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

3.67% chance of exploitation in the next 30 days, higher than 89% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • github.com https://github.com/httplib2/httplib2/security/advisories/GHSA-93xj-8mrv-444m referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
NVD 3.1 7.5 CVSS:3.1/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 httplib2
<0.19.0
0.19.0

Affected products

  • httplib2 httplib2

Classification

Weakness
  • CWE-400 Uncontrolled Resource Consumption

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.