CVE-2026-7383Network attack vector

Crash or code execution via signed size overflow

Published Jun 9, 2026 · Updated Jun 9, 2026

Heap buffer overflow in affected OpenSSL releases allows attackers to corrupt memory via huge Unicode input, causing a crash or code execution. ASN1_mbstring_copy() and ASN1_mbstring_ncopy() compute Unicode destination sizes in signed ints, allowing counts near 2^30 to wrap before allocation and drive a multi-gigabyte overwrite. Reachability requires direct API use or a custom string type plus roughly half a gigabyte of attacker-controlled input; normal X.509 and network paths do not exercise the flaw.

CVSS severity8.1
High
EPSS probability0.80%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Heap buffer overflow in affected OpenSSL releases allows attackers to corrupt memory via huge Unicode input, causing a crash or code execution. ASN1_mbstring_copy() and ASN1_mbstring_ncopy() compute Unicode destination sizes in signed ints, allowing counts near 2^30 to wrap before allocation and drive a multi-gigabyte overwrite. Reachability requires direct API use or a custom string type plus roughly half a gigabyte of attacker-controlled input; normal X.509 and network paths do not exercise the flaw.

The record

CVE
CVE-2026-7383
Published
Jun 9, 2026
Updated
Jun 9, 2026
Vendor
OpenSSL Project
Product
OpenSSL
Classifications
CWE-787, T1203
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

8.1CISA-ADPCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/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-787Out-of-bounds Write
T1203Exploitation for Client Execution

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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