CVE-2026-54163Public exploitNetwork attack vector

XSS via unsanitized CSP directive value interpolation

Published Jul 17, 2026 · Updated Jul 17, 2026

CSP injection in GitHub secure_headers before 7.3.0 allows remote attackers to enable XSS or exfiltrate CSP reports via crafted values. The build_sandbox_list_directive, build_media_type_list_directive, and build_report_to_directive methods interpolate caller-supplied strings without removing semicolons or line breaks, allowing injected directives to precede the configured script-src policy. Exploitation requires an application to pass user-controlled data through the per-request sandbox, plugin_types, or report_to override or append APIs, and XSS execution requires a user to load affected content.

CVSS severity4.7
Medium
EPSS probability0.29%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

CSP injection in GitHub secure_headers before 7.3.0 allows remote attackers to enable XSS or exfiltrate CSP reports via crafted values. The build_sandbox_list_directive, build_media_type_list_directive, and build_report_to_directive methods interpolate caller-supplied strings without removing semicolons or line breaks, allowing injected directives to precede the configured script-src policy. Exploitation requires an application to pass user-controlled data through the per-request sandbox, plugin_types, or report_to override or append APIs, and XSS execution requires a user to load affected content.

The record

CVE
CVE-2026-54163
Published
Jul 17, 2026
Updated
Jul 17, 2026
Vendor
Twitter
Product
secure_headers
Classifications
CWE-79, CWE-113, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jul 17, 2026CVE publishedPublication date reported by the CVE source.
  2. Jul 17, 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=< 7.3.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Twitter · secure_headersversion=< 7.3.0

Published CVSS scores

4.7GitHubCVSS:3.1/AV:N/AC:H/PR:N/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.

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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
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
CWE-113Improper Neutralization of CRLF Sequences in HTTP Headers ('HTTP Request/Response Splitting')
T1190Exploit Public-Facing Application

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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