CVE-2026-46527Public exploitNetwork attack vector

Unauthenticated server crash via empty vector access

Published May 29, 2026 · Updated May 29, 2026

Denial of service in Yuji Hirose cpp-httplib before 0.44.0 allows remote attackers to crash HTTP servers via a malformed X-Forwarded-For header. In get_client_ip(), parsing an empty, comma-only, or whitespace-only header leaves ip_list empty, yet the function calls vector::front() without checking it. The path is reachable only when Server::set_trusted_proxies() has a non-empty list; deployments without trusted proxies do not enter the crash path.

CVSS severity8.7
High
EPSS probability0.33%
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 before 0.44.0 allows remote attackers to crash HTTP servers via a malformed X-Forwarded-For header. In get_client_ip(), parsing an empty, comma-only, or whitespace-only header leaves ip_list empty, yet the function calls vector::front() without checking it. The path is reachable only when Server::set_trusted_proxies() has a non-empty list; deployments without trusted proxies do not enter the crash path.

The record

CVE
CVE-2026-46527
Published
May 29, 2026
Updated
May 29, 2026
Vendor
Yuji Hirose
Product
cpp-httplib
Classifications
CWE-476, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. May 29, 2026CVE publishedPublication date reported by the CVE source.
  2. May 29, 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=< 0.44.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Yuji Hirose · cpp-httplibversion=< 0.44.0

Published CVSS scores

8.7GitHub, Inc.CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
7.5NIST NVDCVSS: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.

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 exploitPublished

Weakness, pattern, technique

CWE-476NULL Pointer Dereference
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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