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Fencer Vulns
medium 6.1

CVE-2021-29272 json

Cross-site scripting in bluemonday

published 2021-03-27 5 y ago modified 2026-06-17 4 mo ago also GHSA-3x58-xr87-2fcj , GO-2022-0762 , EUVD-2021-0925

cvss
6.1
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
0.9%
EPSS 0.9% chance of exploitation in 30 days, percentile 60%
public exploits
0
none known

Summary

bluemonday before 1.0.5 allows XSS because certain Go lowercasing converts an uppercase Cyrillic character, defeating a protection mechanism against the "script" string.

Patch / fix

  • go github.com/microcosm-cc/bluemonday 1.0.5
  • microco bluemonday 1.0.5
  • gitea Alpine 3.12 1.13.7
  • gitea Alpine 3.24, Alpine 3.23, Alpine 3.22 +9 more 1.13.7-r0

alpine advisories ALPINE-CVE-2021-29272

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-2021-29272 updated cvss 5.9

bluemonday: Cross-site scripting via uppercase Cyrillic i

  • Red Hat Advanced Cluster Management for Kubernetes 2 bluemonday
    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

0.93% chance of exploitation in the next 30 days, higher than 60% of all scored CVEs (FIRST EPSS, 2026-11-08).

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
go github.com/microcosm-cc/bluemonday
<1.0.5
1.0.5

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.