CVE-2026-8367Public exploitNetwork attack vector

TLS server impersonation via ignored certificate EKU

Published May 13, 2026 · Updated May 13, 2026

Improper certificate validation in aria2c 1.37.0 and earlier allows remote attackers to impersonate TLS servers during HTTPS downloads. The HTTPS certificate-validation path accepts a trusted X.509 leaf certificate whose Extended Key Usage permits client authentication but not server authentication. Exploitation requires the certificate's private key and control of the victim's connection; successful impersonation exposes or alters downloaded data without interrupting aria2c.

CVSS severity4.8
Medium
EPSS probability0.13%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper certificate validation in aria2c 1.37.0 and earlier allows remote attackers to impersonate TLS servers during HTTPS downloads. The HTTPS certificate-validation path accepts a trusted X.509 leaf certificate whose Extended Key Usage permits client authentication but not server authentication. Exploitation requires the certificate's private key and control of the victim's connection; successful impersonation exposes or alters downloaded data without interrupting aria2c.

The record

CVE
CVE-2026-8367
Published
May 13, 2026
Updated
May 13, 2026
Vendor
aria2 Project
Product
aria2
Classifications
CWE-295, T1557
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. May 13, 2026CVE publishedPublication date reported by the CVE source.
  2. May 13, 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 <=1.37.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

aria2 Project · aria2version=0 <=1.37.0

Published CVSS scores

5.3NIST National Vulnerability DatabaseCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
4.8Tenable Network Security, Inc.CVSS:3.1/AV:N/AC:H/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 exploitPublished

Weakness, pattern, technique

CWE-295Improper Certificate Validation
T1557Adversary-in-the-Middle

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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