CVE-2026-31870Public exploitNetwork attack vector

Remote process crash via malformed Content-Length

Published Mar 11, 2026 · Updated Mar 11, 2026

Uncaught exception in cpp-httplib before 0.37.1 allows remote attackers to crash streaming-client processes via an HTTP response. ClientImpl::open_stream() passes an unvalidated Content-Length value to std::stoull() without catching invalid_argument or out_of_range. The target application must use the httplib::stream API and connect directly, follow a redirect, or accept an intercepted response; ordinary non-streaming requests are unaffected.

CVSS severity7.5
High
EPSS probability0.45%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Uncaught exception in cpp-httplib before 0.37.1 allows remote attackers to crash streaming-client processes via an HTTP response. ClientImpl::open_stream() passes an unvalidated Content-Length value to std::stoull() without catching invalid_argument or out_of_range. The target application must use the httplib::stream API and connect directly, follow a redirect, or accept an intercepted response; ordinary non-streaming requests are unaffected.

The record

CVE
CVE-2026-31870
Published
Mar 11, 2026
Updated
Mar 11, 2026
Vendor
Yuji Hirose
Product
cpp-httplib
Classifications
CWE-248, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Mar 11, 2026CVE publishedPublication date reported by the CVE source.
  2. Mar 11, 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=< 0.37.1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Yuji Hirose · cpp-httplibversion=< 0.37.1

Published CVSS scores

7.5GitHub, Inc.CVSS: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-248Uncaught Exception
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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