CVE-2026-66753Public exploitNetwork attack vector

HTTP response splitting via unvalidated header values

Published Jul 28, 2026 · Updated Aug 14, 2026

HTTP header injection in tiny-http 0.12.0 and earlier allows remote attackers to split responses through crafted header values. The read_next_line routine accepts bare LF bytes in request header values, while Header::from_bytes accepts CRLF and the response writer serializes values verbatim. Exploitation requires a consumer that reflects or forwards attacker-controlled headers, enabling cache poisoning, session fixation, security-header override, or request smuggling against LF-tolerant backends.

CVSS severity6.3
Medium
EPSS probability0.22%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

HTTP header injection in tiny-http 0.12.0 and earlier allows remote attackers to split responses through crafted header values. The read_next_line routine accepts bare LF bytes in request header values, while Header::from_bytes accepts CRLF and the response writer serializes values verbatim. Exploitation requires a consumer that reflects or forwards attacker-controlled headers, enabling cache poisoning, session fixation, security-header override, or request smuggling against LF-tolerant backends.

The record

CVE
CVE-2026-66753
Published
Jul 28, 2026
Updated
Aug 14, 2026
Vendor
tiny-http
Product
tiny-http
Classifications
CWE-113, CWE-93, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jul 28, 2026CVE publishedPublication date reported by the CVE source.
  2. Aug 14, 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 <=0.12.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

tiny-http · tiny-httpversion=0 <=0.12.0

Published CVSS scores

6.3Technical security advisoryCVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/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
T1190Exploit Public-Facing Application

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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