CVE-2025-52887Public exploitNetwork attack vector

Unauthenticated denial of service via unlimited headers

Published Jun 26, 2025 · Updated Jun 26, 2025

Denial of service in Yuji Hirose cpp-httplib 0.21.0 allows remote attackers to crash or hang servers with incomplete HTTP headers. The read_headers function limits each field's length but not the field count, inserting every received field into an unordered multimap while the connection remains open. The flaw is reachable without authentication before request routing, and sustained header input exhausts memory in the hosting process.

CVSS severity7.5
High
EPSS probability0.46%
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 Yuji Hirose cpp-httplib 0.21.0 allows remote attackers to crash or hang servers with incomplete HTTP headers. The read_headers function limits each field's length but not the field count, inserting every received field into an unordered multimap while the connection remains open. The flaw is reachable without authentication before request routing, and sustained header input exhausts memory in the hosting process.

The record

CVE
CVE-2025-52887
Published
Jun 26, 2025
Updated
Jun 26, 2025
Vendor
Yuji Hirose
Product
cpp-httplib
Classifications
CWE-400, T1499
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jun 26, 2025CVE publishedPublication date reported by the CVE source.
  2. Jun 26, 2025Record 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== 0.21.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Yuji Hirose · cpp-httplibversion== 0.21.0

Published CVSS scores

7.5GitHub Security AdvisoryCVSS: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

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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-400Uncontrolled Resource Consumption
T1499Endpoint Denial of Service

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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