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CVE-2026-47733· NVD / CVE Program· CNA GitHub_M

Rocket.Chat: Missing URL protocol sanitization in ImageElement allows javascript: URLs in markdown images

Rocket.Chat is an open-source, secure, fully customizable communications platform. Prior to 8.5.0, the ImageElement component in packages/gazzodown renders user-controlled src values directly into <a href> and <img src> attributes without protocol sanitization. Unlike the analogous LinkSpan component — which uses sanitizeUrl to block javascript:, data:, and vbscript: protocols — ImageElement passes the raw URL through unchanged. An authenticated user can post a markdown image with a javascript: URL that, if clicked on an older browser, would execute arbitrary JavaScript in the viewer's session. This vulnerability is fixed in 8.5.0.

MediumCVSS 4.4 · v3.1—No exploit Fix available
Published
Jun 24, 2026
Updated
Jun 25, 2026
EPSS
0.2% · 7th percentile
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Report tools

JSON

Action score

17

Monitor

Low priority for now.

CVSS
17 / 40 · 4.4 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.2%

CISA SSVC decision

Exploitation
proof of concept
Automatable
no
Technical impact
partial

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD
—
CNA · GitHub_M
4.4
NVD has not scored this yet; the score shown is the CNA’s.

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

Affected systems

—

Versions reported by the vendor

Affected version ranges reported by the assigning authority (GitHub_M). Independent of NVD's CPE analysis and usually ahead of it.

  • RocketChat Rocket.Chat

    • < 8.5.0affected

Same product

rocketchat: all records

Other highest-scoring records for the same primary product.

  • CVE-2026-55666Rocket.Chat: Email Parameter Fallback Leads To Account Takeover Within Apple OAuth
    37Monitor
  • CVE-2026-46423Rocket.Chat: SAML signature validation skipped when IdP certificate field is empty
    37Monitor
  • CVE-2026-45689Rocket.Chat: Pre-Auth NoSQL Injection in OAuth2 Token Endpoint leading to Arbitrary User ATO
    36Monitor
  • CVE-2026-45688Rocket.Chat: Pre-Auth NoSQL Injection in CAS Login Handler leading to Arbitrary CAS/SAML User Session Hijack
    36Monitor
  • CVE-2026-45687Rocket.Chat: Authenticated Arbitrary Data Export Theft via Mass Assignment in sendFileMessage
    34Monitor
  • CVE-2026-45677Rocket.Chat: Lack of SAML Signature Check During Logout Could Lead To DoS
    34Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
RocketChat Rocket.Chat8.5.0 · descriptionVendor (CNA)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

EPSS, last 120 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

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Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

  • CVE-2026-556660 days apartRocket.Chat: Email Parameter Fallback Leads To Account Takeover Within Apple OAuth
    37Monitor
  • CVE-2026-557590 days apartRocket.Chat: Apple Sign-In skips JWT claims validation, allowing expired and cross-audience token replay
    29Monitor

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

Attack conditions

  • Anyone who can reach it over the internet can trigger it.
  • A low-privileged account is enough.
  • A user must open a link or visit a page.
  • Special conditions such as timing or configuration are required.

If successful

Confidentiality
low · data can be read
Integrity
low · data or configuration can be modified
Availability
none

Impact can extend beyond the vulnerable component (scope changes).

Attack vector
Network
Attack complexity
High
Privileges required
Low
User interaction
Required
Scope
Changed
Confidentiality impact
Low
Integrity impact
Low
Availability impact
None

Weakness class (CWE)

CWE-79 · Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

CVSS vector

CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:C/C:L/I:L/A:N

nvd-secondary

Root cause

User content is inserted into the page as HTML. The browser interprets the content as code rather than data.

The bug in code

The whole CWE-79 class

A representative example of this vulnerability class. Not the vendor's source code; it shows the faulty pattern and its fix.

Vulnerable

ts
commentEl.innerHTML = comment.body;

Fixed

ts
commentEl.textContent = comment.body;

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

ATT&CK techniques

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Noroxi analysis

No Noroxi analysis for this record yet

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Change log

  1. Fix✗ → ✓

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References

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records