CVE-2026-58657Public exploitNetwork attack vector

Stored CSS injection via unchecked resize parameters

Published Jul 8, 2026 · Updated Jul 8, 2026

Stored CSS injection in Grav before 2.0.0 allows remote authenticated users to alter rendered pages through crafted Markdown image resize parameters. The resize() path in Excerpts::processMediaActions() passes semicolon-delimited width and height values to styleAttributes, which serializes them into the image's inline CSS without numeric validation. Page-edit rights are required, and the payload takes effect when a reviewer or administrator renders the page or preview, enabling persistent overlays and UI redress without JavaScript execution.

CVSS severity4.8
Medium
EPSS probability0.37%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Stored CSS injection in Grav before 2.0.0 allows remote authenticated users to alter rendered pages through crafted Markdown image resize parameters. The resize() path in Excerpts::processMediaActions() passes semicolon-delimited width and height values to styleAttributes, which serializes them into the image's inline CSS without numeric validation. Page-edit rights are required, and the payload takes effect when a reviewer or administrator renders the page or preview, enabling persistent overlays and UI redress without JavaScript execution.

The record

CVE
CVE-2026-58657
Published
Jul 8, 2026
Updated
Jul 8, 2026
Vendor
Grav
Product
Grav
Classifications
CWE-79, T1565.001
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Jul 8, 2026CVE publishedPublication date reported by the CVE source.
  2. Jul 8, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=2.0.0-rc.9 <2.0.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Grav · Gravversion=2.0.0-rc.9 <2.0.0

Published CVSS scores

4.8GitHubCVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:C/C:L/I:L/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
T1565.001Stored Data Manipulation

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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