CVE-2026-4271Public exploitNetwork attack vector

Application crash via freed HTTP/2 callback object

Published Mar 17, 2026 · Updated Mar 17, 2026

Use-after-free in the libsoup HTTP/2 server allows remote attackers to crash applications with crafted requests that fail authentication. The on_frame_recv_callback() path emits got-headers signals while retaining an IO pointer; a disconnecting handler frees its SoupServerMessageIOHTTP2 object before execution resumes. Exploitation requires an HTTP/2 service whose authentication-failure handler disconnects the client, and the bounded consequence is an application crash.

CVSS severity5.3
Medium
EPSS probability0.83%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Use-after-free in the libsoup HTTP/2 server allows remote attackers to crash applications with crafted requests that fail authentication. The on_frame_recv_callback() path emits got-headers signals while retaining an IO pointer; a disconnecting handler frees its SoupServerMessageIOHTTP2 object before execution resumes. Exploitation requires an HTTP/2 service whose authentication-failure handler disconnects the client, and the bounded consequence is an application crash.

The record

CVE
CVE-2026-4271
Published
Mar 17, 2026
Updated
Mar 17, 2026
Vendor
389 Directory Server
Product
Red Hat Enterprise Linux 6
Classifications
CWE-416, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Mar 17, 2026CVE publishedPublication date reported by the CVE source.
  2. Mar 17, 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?

Affected versions are unavailable in this record. Check the vendor advisory for version and patch details.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

389 Directory Server · Red Hat Enterprise Linux 6Affected versions are unavailable in this record.
389 Directory Server · Red Hat Enterprise Linux 10Affected versions are unavailable in this record.
389 Directory Server · Red Hat Enterprise Linux 7Affected versions are unavailable in this record.
389 Directory Server · Red Hat Enterprise Linux 9Affected versions are unavailable in this record.
389 Directory Server · Red Hat Enterprise Linux 8Affected versions are unavailable in this record.

Published CVSS scores

7.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
5.3Red Hat, Inc.CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

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-416Use After Free
T1499.004Endpoint Denial of Service: Application or System Exploitation

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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