CVE-2026-28898Network attack vector

Unauthenticated request smuggling via unvalidated pseudo-headers

Published Jun 25, 2026 · Updated Jun 25, 2026

Request smuggling in Apple SwiftNIO HTTP/2 before 1.44.1 allows remote attackers to inject backend requests via crafted pseudo-headers. HTTP2FramePayloadToHTTP1ServerCodec and HTTP2ToHTTP1ServerCodec copied CR, LF, or NUL bytes from pseudo-header values into translated HTTP/1.1 messages without validation. Exposure requires a server that translates attacker-controlled HTTP/2 traffic to HTTP/1.1 for a backend, enabling injected headers or entirely smuggled requests.

CVSS severity5.3
Medium
EPSS probability0.31%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Request smuggling in Apple SwiftNIO HTTP/2 before 1.44.1 allows remote attackers to inject backend requests via crafted pseudo-headers. HTTP2FramePayloadToHTTP1ServerCodec and HTTP2ToHTTP1ServerCodec copied CR, LF, or NUL bytes from pseudo-header values into translated HTTP/1.1 messages without validation. Exposure requires a server that translates attacker-controlled HTTP/2 traffic to HTTP/1.1 for a backend, enabling injected headers or entirely smuggled requests.

The record

CVE
CVE-2026-28898
Published
Jun 25, 2026
Updated
Jun 25, 2026
Vendor
Apple
Product
SwiftNIO HTTP/2
Classifications
CWE-444, CWE-116, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jun 25, 2026CVE publishedPublication date reported by the CVE source.
  2. Jun 25, 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 <1.44.1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Apple · SwiftNIO HTTP/2version=0 <1.44.1

Published CVSS scores

5.3GitHub Advisory DatabaseCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
5.3CISA-ADPCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A: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.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-444Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')
CWE-116Improper Encoding or Escaping of Output
T1190Exploit Public-Facing Application

Public exploit references

No public exploit references are available in this record.

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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