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Fencer Intel
medium 6.3

CVE-2026-84463 json

Zammad: Stored HTML injection in Knowledge Base video widget enables forced session switching via unescaped iframe attribute

published 3mo ago modified last mo. also EUVD-2026-87264 , GHSA-cxjg-4gmf-5xqc

Unreviewed: the maintainers' own advisory

Published by the maintainers on their GitHub repository zammad/zammad. GitHub has not reviewed it into the GitHub Advisory Database, so the affected packages and versions are the maintainers' word. Read the full advisory on GitHub.

cvss
6.3
version 4.0, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.2%
EPSS 0.2% chance of exploitation in 30 days, percentile 4%
public exploits
0
none known

Summary

Zammad is a web based open source helpdesk/customer support system. Prior to 7.1.2, a user with Knowledge Base editing rights for a category can embed a video widget in a published answer with a specially crafted value. When the answer is rendered, that value is inserted into the page's HTML without being escaped for its attribute context, allowing it to break out and inject additional HTML into the page. When another user who has permission to switch between user sessions views the affected answer, the injected HTML causes their browser to silently send a request to Zammad's session-switching endpoint using their own active credentials. This results in switching their session to an account chosen by the person who wrote the Knowledge Base answer. No action is required from the viewer beyond opening the published answer. This issue is fixed in version 7.1.2.

Patch / fix

  • zammad zammad 7.1.2

Is CVE-2026-84463 in your stack? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.

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CISA SSVC

Exploitation
none
Automatable
no
Technical impact
partial
Assessed
last mo.

Exploit prediction

0.15% chance of exploitation in the next 30 days, higher than 4% of all scored CVEs (FIRST EPSS, 2026-11-11).

CVSS scores

assigned by version score vector
CNA 4.0 6.3 CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:P/VC:N/VI:N/VA:N/SC:H/SI:H/SA:N
CNA 4.0 6.3 CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:P/VC:N/VI:N/VA:N/SC:H/SI:H/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Affected products

  • zammad zammad

Classification

Weakness
  • CWE-79 Improper Neutralization of Input During Web Page Generation
  • CWE-352 Cross-Site Request Forgery
  • CWE-838 Inappropriate Encoding for Output Context

References

Sources

Fencer Intel 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.

The maintainers of zammad/zammad published their own advisory on GitHub. Reviewed sources take precedence over it.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.