CVE-2026-34180Network attack vector

Application crash via ASN.1 content-length truncation

Published Jun 9, 2026 · Updated Jun 9, 2026

Out-of-bounds read in OpenSSL affected releases allows remote attackers to crash applications using crafted DER-encoded ASN.1 data. The ASN.1 decoder truncates primitive-element lengths above 2 GB, then can scan for a zero byte beyond the allocated input buffer. Reachability requires a 64-bit Unix-like application to pass attacker-supplied data directly to a d2i_* decoder; BIO-based command-line tools, Windows, 32-bit systems, and FIPS modules are excluded.

CVSS severity7.5
High
EPSS probability1.03%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Out-of-bounds read in OpenSSL affected releases allows remote attackers to crash applications using crafted DER-encoded ASN.1 data. The ASN.1 decoder truncates primitive-element lengths above 2 GB, then can scan for a zero byte beyond the allocated input buffer. Reachability requires a 64-bit Unix-like application to pass attacker-supplied data directly to a d2i_* decoder; BIO-based command-line tools, Windows, 32-bit systems, and FIPS modules are excluded.

The record

CVE
CVE-2026-34180
Published
Jun 9, 2026
Updated
Jun 9, 2026
Vendor
OpenSSL Project
Product
OpenSSL
Classifications
CWE-125, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jun 9, 2026CVE publishedPublication date reported by the CVE source.
  2. Jun 9, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=1.0.2 <1.0.2zq
  2. Affected versionversion=1.1.1 <1.1.1zh
  3. Affected versionversion=3.0.0 <3.0.21
  4. Affected versionversion=3.4.0 <3.4.6
  5. Affected versionversion=3.5.0 <3.5.7
  6. Affected versionversion=3.6.0 <3.6.3
  7. Affected versionversion=4.0.0 <4.0.1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

OpenSSL Project · OpenSSLversion=1.0.2 <1.0.2zq; version=1.1.1 <1.1.1zh; version=3.0.0 <3.0.21; version=3.4.0 <3.4.6; version=3.5.0 <3.5.7; version=3.6.0 <3.6.3; version=4.0.0 <4.0.1

Published CVSS scores

7.5CISA-ADPCVSS:3.1/AV:N/AC:L/PR:N/UI:N/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.

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

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-125Out-of-bounds Read
T1499.004Application or System Exploitation

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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