CVE-2025-66373Network attack vector

HTTP request smuggling via mismatched chunk size

Published Dec 4, 2025 · Updated Dec 8, 2025

HTTP request smuggling in Akamai Ghost before 2025-11-17 allows remote attackers to send hidden requests through CDN edge servers. Akamai Ghost forwards an invalid chunked body and surplus bytes when the declared chunk size differs from the following data length. Exploitation requires an origin server that interprets the forwarded invalid request and surplus bytes as a second request, enabling hidden origin requests.

CVSS severity4.8
Medium
EPSS probability0.26%
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 Akamai Ghost before 2025-11-17 allows remote attackers to send hidden requests through CDN edge servers. Akamai Ghost forwards an invalid chunked body and surplus bytes when the declared chunk size differs from the following data length. Exploitation requires an origin server that interprets the forwarded invalid request and surplus bytes as a second request, enabling hidden origin requests.

The record

CVE
CVE-2025-66373
Published
Dec 4, 2025
Updated
Dec 8, 2025
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-444, CAPEC-33, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Dec 4, 2025CVE publishedPublication date reported by the CVE source.
  2. Dec 8, 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?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

4.8NVDCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/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 exploitUnconfirmed

Weakness, pattern, technique

CWE-444Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')
CAPEC-33HTTP Request 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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