CVE-2026-54387Public exploitNetwork attack vector

Backend request injection via CL/TE desynchronization

Published Jun 17, 2026 · Updated Jun 17, 2026

HTTP request smuggling in Tinyproxy 1.11.3 and earlier allows remote attackers to inject arbitrary backend requests via CL/TE conflicts. In process_client_headers(), Tinyproxy forwards both Content-Length and Transfer-Encoding while using Content-Length to read the body, so the backend parses a different boundary. Network access to the proxy is sufficient; injected requests enable cache poisoning, access-control bypass, and request hijacking.

CVSS severity9.3
Critical
EPSS probability0.44%
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 Tinyproxy 1.11.3 and earlier allows remote attackers to inject arbitrary backend requests via CL/TE conflicts. In process_client_headers(), Tinyproxy forwards both Content-Length and Transfer-Encoding while using Content-Length to read the body, so the backend parses a different boundary. Network access to the proxy is sufficient; injected requests enable cache poisoning, access-control bypass, and request hijacking.

The record

CVE
CVE-2026-54387
Published
Jun 17, 2026
Updated
Jun 17, 2026
Vendor
Tinyproxy
Product
Tinyproxy
Classifications
CWE-444, CAPEC-33, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jun 17, 2026CVE publishedPublication date reported by the CVE source.
  2. Jun 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=0 <=1.11.3

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Tinyproxy · Tinyproxyversion=0 <=1.11.3

Published CVSS scores

9.1VulnCheckCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
9.3VulnCheckCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA: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-444Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')
CAPEC-33HTTP Request Smuggling
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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