CVE-2025-47905Network attack vector

Cache poisoning via skipped CRLF chunk delimiters

Published May 13, 2025 · Updated May 29, 2025

HTTP request smuggling in Varnish Cache allows remote attackers to poison downstream caches via malformed HTTP/1 chunked requests. The HTTP/1 chunk parser incorrectly permits CRLF bytes to be skipped when delimiting chunk boundaries, causing inconsistent message framing. Exploitation requires a downstream cache or WAF that accepts the malformed request; consequences are malicious cached content or bypassed request inspection.

CVSS severity5.4
Medium
EPSS probability0.36%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

HTTP request smuggling in Varnish Cache allows remote attackers to poison downstream caches via malformed HTTP/1 chunked requests. The HTTP/1 chunk parser incorrectly permits CRLF bytes to be skipped when delimiting chunk boundaries, causing inconsistent message framing. Exploitation requires a downstream cache or WAF that accepts the malformed request; consequences are malicious cached content or bypassed request inspection.

The record

CVE
CVE-2025-47905
Published
May 13, 2025
Updated
May 29, 2025
Vendor
Varnish Software
Product
Varnish Cache
Classifications
CWE-444, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. May 13, 2025CVE publishedPublication date reported by the CVE source.
  2. May 29, 2025Record 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=0 <6.0.14 LTS
  2. Affected versionversion=7.0.0 <7.6.3
  3. Affected versionversion=7.7.0 <7.7.1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Varnish Software · Varnish Cacheversion=0 <6.0.14 LTS; version=7.0.0 <7.6.3; version=7.7.0 <7.7.1

Published CVSS scores

5.4MITRECVSS:3.1/AV:N/AC:H/PR:N/UI:N/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
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-444Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')
T1190Exploit Public-Facing Application

Public exploit references

No public exploit references are available in this record.

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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