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Fencer Vulns
medium 6.1

CVE-2020-6802 json

XSS in Bleach when noscript and raw tag whitelisted

published 2020-02-24 6 y ago modified 2026-07-08 4 mo ago also GHSA-q65m-pv3f-wr5r , PYSEC-2020-27 , EUVD-2020-0054

cvss
6.1
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
1.7%
EPSS 1.7% chance of exploitation in 30 days, percentile 77%
public exploits
0
none known

Summary

In Mozilla Bleach before 3.11, a mutation XSS affects users calling bleach.clean with noscript and a raw tag in the allowed/whitelisted tags option.

Patch / fix

  • pypi bleach 3.1.1
  • mozilla bleach 3.1.1
  • python-bleach Debian 14, Debian 13, Debian 12 3.1.1-1

debian advisories DEBIAN-CVE-2020-6802

  • python-bleach Ubuntu Pro 18.04 LTS 2.1.2-1ubuntu0.1~esm1

ubuntu advisories UBUNTU-CVE-2020-6802

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-bleach openSUSE Tumbleweed 6.4.0-1.1
  • python-bleach openSUSE Tumbleweed 6.1.0-1.5
  • weblate openSUSE Tumbleweed 4.8.1-1.1
  • python-bleach Package Hub 15 SP1 3.1.1-bp151.4.4.1
  • python-bleach openSUSE Leap 15.1 3.1.1-lp151.3.6.1

opensuse advisories openSUSE-SU-2026:11323-1openSUSE-SU-2024:14134-1openSUSE-SU-2024:11507-1openSUSE-SU-2020:0325-1openSUSE-SU-2020:0308-1

  • py3-bleach Alpine 3.24, Alpine 3.23, Alpine 3.22 +11 more 3.1.1-r0

alpine advisories ALPINE-CVE-2020-6802

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

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-2020-6802 updated cvss 6.1

python-bleach: mutation XSS vulnerability

  • Red Hat All currently supported Red Hat products
    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

1.73% chance of exploitation in the next 30 days, higher than 77% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • checkmarx.com https://www.checkmarx.com/blog/vulnerabilities-discovered-in-mozilla-bleach referenced PoC, tagged "exploit" by a source, unverified
  • advisory.checkmarx.net https://advisory.checkmarx.net/advisory/CX-2020-4276 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
NVD 3.1 6.1 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
NVD 2.0 4.3 AV:N/AC:M/Au:N/C:N/I:P/A:N
GitHub 3.1 6.1 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

Affected packages

ecosystem package affected fixed in
pypi bleach
<3.1.1
3.1.1

Affected products

  • n/a Mozilla Bleach

Classification

Weakness
  • CWE-79 Improper Neutralization of Input During Web Page Generation

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.