CVE-2026-77341Public exploitNetwork attack vector

HTTP response splitting via unvalidated chunked trailers

Published Aug 27, 2026 · Updated Aug 27, 2026

CRLF injection in cpp-httplib 0.49.0 allows remote attackers to split HTTP responses through attacker-influenced chunked trailers. The done_with_trailer lambda in write_content_chunked writes trailer names and values to the socket without field-name or field-value validation. Exploitation requires an application to place attacker-influenced data in a chunked-response trailer, enabling forged response headers or a second response.

CVSS severity5.3
Medium
EPSS probability0.27%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

CRLF injection in cpp-httplib 0.49.0 allows remote attackers to split HTTP responses through attacker-influenced chunked trailers. The done_with_trailer lambda in write_content_chunked writes trailer names and values to the socket without field-name or field-value validation. Exploitation requires an application to place attacker-influenced data in a chunked-response trailer, enabling forged response headers or a second response.

The record

CVE
CVE-2026-77341
Published
Aug 27, 2026
Updated
Aug 27, 2026
Vendor
Yuji Hirose
Product
cpp-httplib
Classifications
CWE-113, CWE-93
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 27, 2026CVE publishedPublication date reported by the CVE source.
  2. Aug 27, 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=>= 0.49.0, < 0.50.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Yuji Hirose · cpp-httplibversion=>= 0.49.0, < 0.50.0

Published CVSS scores

5.3GitHub, Inc.CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:L/VA:N/SC:L/SI:L/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.

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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-113Improper Neutralization of CRLF Sequences in HTTP Headers ('HTTP Request/Response Splitting')
CWE-93Improper Neutralization of CRLF Sequences ('CRLF Injection')

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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