CVE-2026-93894Network attack vector

Child-process restart via VCL workspace overflow

Published Sep 18, 2026 · Updated Sep 18, 2026

Workspace buffer overflow in Vinyl Cache before 9.0.2 and affected Varnish Cache releases allows remote attackers to restart the child. The VCL string .upper() and .lower() methods exhaust the remaining workspace and write beyond its buffer while transforming an oversized string. Exploitation requires knowledge of the deployed VCL and a request string sized to fill the call-site workspace without exceeding configured request limits; success interrupts service by crashing or asserting the child before its automatic restart.

CVSS severity2.3
Low
EPSS probability0.36%
Next 30 days · Oct 19, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Workspace buffer overflow in Vinyl Cache before 9.0.2 and affected Varnish Cache releases allows remote attackers to restart the child. The VCL string .upper() and .lower() methods exhaust the remaining workspace and write beyond its buffer while transforming an oversized string. Exploitation requires knowledge of the deployed VCL and a request string sized to fill the call-site workspace without exceeding configured request limits; success interrupts service by crashing or asserting the child before its automatic restart.

The record

CVE
CVE-2026-93894
Published
Sep 18, 2026
Updated
Sep 18, 2026
Vendor
Varnish Software
Product
Varnish Cache
Classifications
CWE-787, T1499
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Sep 18, 2026CVE publishedPublication date reported by the CVE source.
  2. Sep 18, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=0 <c5078ae575201b05ae8674a90ddb19ffe7f4b439
  2. Affected versionversion=6.3.0 <=8.0.2
  3. Affected versionversion=9.0.0 <9.0.4

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Varnish Software · Varnish Cacheversion=0 <c5078ae575201b05ae8674a90ddb19ffe7f4b439; version=6.3.0 <=8.0.2; version=9.0.0 <9.0.4
Vinyl Cache Project · Vinyl Cacheversion=0 <9.0.2; version=0 <90f5bacc14b2404e6cc349ba015f0f73b8515136

Published CVSS scores

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

Activity data is delayed. The latest report is Sep 28, 2026.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 22, 2026Sep 28, 2026
Latest reporting daySep 28, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-787Out-of-bounds Write
T1499Endpoint Denial of Service

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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