CVE-2021-38512Network attack vector

Credential disclosure via HTTP request smuggling

Published Aug 10, 2021 · Updated Aug 4, 2024

HTTP request smuggling in actix-http before 3.0.0-beta.9 allows remote attackers to disclose credentials via crafted HTTP/1 requests. The HTTP/1 parser accepts ambiguous or invalid request framing instead of consistently rejecting conflicting length indicators, allowing desynchronization with a front-end proxy. Exploitation requires a vulnerable intermediary and backend connection reuse; successful desynchronization can expose internal or user data, including credentials.

CVSS severity7.5
High
EPSS probability1.81%
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 actix-http before 3.0.0-beta.9 allows remote attackers to disclose credentials via crafted HTTP/1 requests. The HTTP/1 parser accepts ambiguous or invalid request framing instead of consistently rejecting conflicting length indicators, allowing desynchronization with a front-end proxy. Exploitation requires a vulnerable intermediary and backend connection reuse; successful desynchronization can expose internal or user data, including credentials.

The record

CVE
CVE-2021-38512
Published
Aug 10, 2021
Updated
Aug 4, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-444, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 10, 2021CVE 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?

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

7.5GitLab Advisory Database (RustSec)CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/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')
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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