CVE-2026-11352Public exploitNetwork attack vector

Client hang via uncounted zero-length datagrams

Published Jul 3, 2026 · Updated Jul 3, 2026

Denial of service in curl and libcurl 8.18.0 through 8.20.0 allows remote attackers controlling an HTTP/3 server to hang the client. The QUIC UDP receive helper discards zero-length datagrams without incrementing the per-call packet counter, so its receive loop never reaches its limit. Exploitation requires a connected HTTP/3 peer on a platform that provides recvmmsg(), and it stalls the affected client without reported data exposure or modification.

CVSS severity7.5
High
EPSS probability0.71%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Denial of service in curl and libcurl 8.18.0 through 8.20.0 allows remote attackers controlling an HTTP/3 server to hang the client. The QUIC UDP receive helper discards zero-length datagrams without incrementing the per-call packet counter, so its receive loop never reaches its limit. Exploitation requires a connected HTTP/3 peer on a platform that provides recvmmsg(), and it stalls the affected client without reported data exposure or modification.

The record

CVE
CVE-2026-11352
Published
Jul 3, 2026
Updated
Jul 3, 2026
Vendor
curl
Product
curl
Classifications
CWE-835, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jul 3, 2026CVE publishedPublication date reported by the CVE source.
  2. Jul 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=8.18.0 <=8.18.0
  2. Affected versionversion=8.19.0 <=8.19.0
  3. Affected versionversion=8.20.0 <=8.20.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

curl · curlversion=8.18.0 <=8.18.0; version=8.19.0 <=8.19.0; version=8.20.0 <=8.20.0

Published CVSS scores

7.5CISA-ADPCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

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-835Loop with Unreachable Exit Condition ('Infinite Loop')
T1499.004Application or System Exploitation

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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