CVE-2026-29085Network attack vector

SSE field injection via unfiltered CR/LF

Published Mar 4, 2026 · Updated Mar 4, 2026

Injection in Hono before 4.12.4 allows remote attackers to alter SSE event frames through untrusted streamSSE() control fields. writeSSE() joined event, id, and retry values into newline-delimited frames without rejecting embedded CR or LF, so a value could introduce extra SSE fields. Reachability requires an application to pass attacker-controlled data into those fields; the bounded consequence is altered event-stream structure and handling.

CVSS severity6.5
Medium
EPSS probability0.24%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Injection in Hono before 4.12.4 allows remote attackers to alter SSE event frames through untrusted streamSSE() control fields. writeSSE() joined event, id, and retry values into newline-delimited frames without rejecting embedded CR or LF, so a value could introduce extra SSE fields. Reachability requires an application to pass attacker-controlled data into those fields; the bounded consequence is altered event-stream structure and handling.

The record

CVE
CVE-2026-29085
Published
Mar 4, 2026
Updated
Mar 4, 2026
Vendor
Hono
Product
Hono
Classifications
CWE-74, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Mar 4, 2026CVE publishedPublication date reported by the CVE source.
  2. Mar 4, 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=< 4.12.4

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Hono · Honoversion=< 4.12.4

Published CVSS scores

6.5GitHubCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/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.

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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 exploitUnconfirmed

Weakness, pattern, technique

CWE-74Improper Neutralization of Special Elements in Output Used by a Downstream Component ('Injection')
T1190Exploit Public-Facing Application

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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