CVE-2020-5216Network attack vector

CSP header injection via unsanitized newlines

Published Jan 23, 2020 · Updated Aug 4, 2024

Header injection in Twitter secure_headers allows remote authenticated users to add CSP headers through crafted dynamic directives. The content-security-policy builder passes newline-containing source-list values to Rails without removing line breaks, so Rails emits each remainder as another Content-Security-Policy header. Exploitation requires an application to feed attacker-controlled data into a dynamic override and user interaction; the effect is limited to extra CSP headers in the affected response.

CVSS severity4.4
Medium
EPSS probability1.08%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Header injection in Twitter secure_headers allows remote authenticated users to add CSP headers through crafted dynamic directives. The content-security-policy builder passes newline-containing source-list values to Rails without removing line breaks, so Rails emits each remainder as another Content-Security-Policy header. Exploitation requires an application to feed attacker-controlled data into a dynamic override and user interaction; the effect is limited to extra CSP headers in the affected response.

The record

CVE
CVE-2020-5216
Published
Jan 23, 2020
Updated
Aug 4, 2024
Vendor
Twitter
Product
secure_headers
Classifications
CWE-113
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Jan 23, 2020CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 2024Record 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=< 3.9.0
  2. Affected versionversion=>= 5.0.0, < 5.2.0
  3. Affected versionversion=>= 6.0.0, < 6.3.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Twitter · secure_headersversion=< 3.9.0; version=>= 5.0.0, < 5.2.0; version=>= 6.0.0, < 6.3.0

Published CVSS scores

4.4GitHub CNACVSS:3.1/AV:N/AC:H/PR:L/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 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-113Improper Neutralization of CRLF Sequences in HTTP Headers ('HTTP Response Splitting')

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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