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Fencer Intel
medium 4.7

CVE-2026-48164 json

Collabora Online: Reflected HTML injection through host_session_id

published 4mo ago modified 12d ago also EUVD-2026-114089 , GHSA-wgmm-q3ch-64jj

Unreviewed: the maintainers' own advisory

Published by the maintainers on their GitHub repository CollaboraOnline/online. 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
4.7
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.3%
EPSS 0.3% chance of exploitation in 30 days, percentile 25%
public exploits
0
none known

Summary

Collabora Online is a collaborative online office suite based on LibreOffice technology. Prior to 24.04.18 and 25.04.11, the `host_session_id` query/form parameter is substituted into the `cool.html` editor page without HTML encoding, unlike parameters passed through the existing variable-encoding mechanism. An attacker who induces a victim to load a crafted URL can inject HTML and, in the absence of an effective `Content Security Policy`, execute scripts in the Collabora Online iframe's origin, exposing the session authentication token and page contents. A reverse proxy that preserves the `Content Security Policy` header sent by `coolwsd` mitigates the script-execution scenario. This issue is fixed in versions 24.04.18 and 25.04.11.

Patch / fix

  • collabora online 24.04.18, 25.04.11
  • collaboraoffice collabora_online 24.04.18, 25.04.11
  • collaboraoffice richdocumentscode 24.04.18, 25.04.11

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CISA SSVC

Exploitation
none
Automatable
no
Technical impact
partial
Assessed
12d ago

Exploit prediction

0.33% chance of exploitation in the next 30 days, higher than 25% of all scored CVEs (FIRST EPSS, 2026-11-11).

CVSS scores

assigned by version score vector
CNA 3.1 4.7 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:N/I:L/A:N

Affected products

  • CollaboraOnline online

Classification

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

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 CollaboraOnline/online 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.