CVE-2026-45271

Application crash via unbounded ASN.1 recursion

Published Aug 21, 2026 · Updated Aug 25, 2026

Denial of service in H2O picotls before commit c14231d allows local users to crash an application via crafted DER input. The minicrypto ASN.1 validator recursively descends into constructed elements without limiting nesting depth, so deeply nested DER exhausts the process stack. Exploitation requires an application to load attacker-controlled PKCS#8 data or pass untrusted DER to the public validation API; the OpenSSL backend is unaffected.

CVSS severity5.5
Medium
EPSS probability0.11%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Denial of service in H2O picotls before commit c14231d allows local users to crash an application via crafted DER input. The minicrypto ASN.1 validator recursively descends into constructed elements without limiting nesting depth, so deeply nested DER exhausts the process stack. Exploitation requires an application to load attacker-controlled PKCS#8 data or pass untrusted DER to the public validation API; the OpenSSL backend is unaffected.

The record

CVE
CVE-2026-45271
Published
Aug 21, 2026
Updated
Aug 25, 2026
Vendor
H2O Project
Product
picotls
Classifications
CWE-835, T1499.004
Attack vector
local
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 21, 2026CVE publishedPublication date reported by the CVE source.
  2. Aug 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=< c14231d801407640bc42c2dcf92783409ea6a7c7

What conditions does exploitation require?

Attack vectorlocal
Required privilegesunauthenticated

What is affected?

H2O Project · picotlsversion=< c14231d801407640bc42c2dcf92783409ea6a7c7

Published CVSS scores

5.5GitHubCVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H

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)
Vectorlocal
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-835Loop with Unreachable Exit Condition ('Infinite Loop')
T1499.004Endpoint Denial of Service: Application or System Exploitation

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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