CVE-2026-63382Public exploitNetwork attack vector

Request smuggling via inconsistent HTTP framing

Published Aug 20, 2026 · Updated Aug 20, 2026

HTTP request smuggling in Libevent before 2.1.13 and 2.2.2-alpha allows remote attackers to smuggle requests via malformed HTTP/1.1 framing. In evhttp's http.c parser, evhttp_find_header() honors only the first Transfer-Encoding header, the older whole-string check misses comma-separated values ending in chunked, and evhttp_handle_chunked_read accepts bare LF chunk terminators, letting a proxy and backend disagree on request boundaries. Exposure requires Libevent to sit behind a proxy or intermediary that parses the same request differently; successful desynchronization can bypass front-end access controls or poison shared caches.

CVSS severity9.2
Critical
EPSS probability0.59%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

HTTP request smuggling in Libevent before 2.1.13 and 2.2.2-alpha allows remote attackers to smuggle requests via malformed HTTP/1.1 framing. In evhttp's http.c parser, evhttp_find_header() honors only the first Transfer-Encoding header, the older whole-string check misses comma-separated values ending in chunked, and evhttp_handle_chunked_read accepts bare LF chunk terminators, letting a proxy and backend disagree on request boundaries. Exposure requires Libevent to sit behind a proxy or intermediary that parses the same request differently; successful desynchronization can bypass front-end access controls or poison shared caches.

The record

CVE
CVE-2026-63382
Published
Aug 20, 2026
Updated
Aug 20, 2026
Vendor
Libevent
Product
Libevent
Classifications
CWE-444, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 20, 2026CVE publishedPublication date reported by the CVE source.
  2. Aug 20, 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=< 2.1.13
  2. Affected versionversion=>= 2.2.0-alpha, < 2.2.2-alpha

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Libevent · Libeventversion=< 2.1.13; version=>= 2.2.0-alpha, < 2.2.2-alpha

Published CVSS scores

9.2GitHub CNACVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:L/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-444Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')
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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