CVE-2026-50052Network attack vector

Authentication bypass via HTTP/2 request desynchronization

Published Jun 3, 2026 · Updated Jun 3, 2026

HTTP request smuggling in affected Vinyl Cache and Varnish Cache releases allows remote attackers to desynchronize backend requests. The HTTP/2 HPACK parser in cache_http2_hpack.c accepts injected invalid header lines that a backend can interpret as a second request. Exploitation requires default-disabled +http2 and an exploitable URL accepting a request body; successful desynchronization can poison cached responses or cross backend authentication boundaries.

CVSS severity2.3
Low
EPSS probability0.40%
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 affected Vinyl Cache and Varnish Cache releases allows remote attackers to desynchronize backend requests. The HTTP/2 HPACK parser in cache_http2_hpack.c accepts injected invalid header lines that a backend can interpret as a second request. Exploitation requires default-disabled +http2 and an exploitable URL accepting a request body; successful desynchronization can poison cached responses or cross backend authentication boundaries.

The record

CVE
CVE-2026-50052
Published
Jun 3, 2026
Updated
Jun 3, 2026
Vendor
Varnish Software
Product
Varnish Cache
Classifications
CWE-444, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jun 3, 2026CVE publishedPublication date reported by the CVE source.
  2. Jun 3, 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=9.0.0 <=9.0.2

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Varnish Software · Varnish Cacheversion=9.0.0 <=9.0.2
Vinyl Cache Project · Vinyl Cacheversion=6.0.14 <=6.0.17; version=7.6.0 <=8.0.1; version=9.0.0

Published CVSS scores

2.3MITRECVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:P/VC:L/VI:N/VA:N/SC:L/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.

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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