CVE-2026-34181Network attack vector

Credential forgery via one-byte PBMAC1 keys

Published Jun 9, 2026 · Updated Jun 9, 2026

Integrity validation in OpenSSL 3.4.0 through 3.4.5, 3.5.0 through 3.5.6, 3.6.0 through 3.6.2, and 4.0.0 allows credential forgery. PBMAC1_PBKDF2_HMAC in crypto/pkcs12/p12_mutl.c accepts an attacker-specified PBKDF2 key length as low as one byte instead of rejecting values below 20 bytes. A password-authenticating service that accepts unencrypted PKCS#12 files can accept attacker-controlled credentials with a 1-in-256 probability; FIPS modules are outside the affected boundary.

CVSS severity7.4
High
EPSS probability0.24%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Integrity validation in OpenSSL 3.4.0 through 3.4.5, 3.5.0 through 3.5.6, 3.6.0 through 3.6.2, and 4.0.0 allows credential forgery. PBMAC1_PBKDF2_HMAC in crypto/pkcs12/p12_mutl.c accepts an attacker-specified PBKDF2 key length as low as one byte instead of rejecting values below 20 bytes. A password-authenticating service that accepts unencrypted PKCS#12 files can accept attacker-controlled credentials with a 1-in-256 probability; FIPS modules are outside the affected boundary.

The record

CVE
CVE-2026-34181
Published
Jun 9, 2026
Updated
Jun 9, 2026
Vendor
OpenSSL Project
Product
OpenSSL
Classifications
CWE-354, T1556
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

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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=3.4.0 <3.4.6
  2. Affected versionversion=3.5.0 <3.5.7
  3. Affected versionversion=3.6.0 <3.6.3
  4. Affected versionversion=4.0.0 <4.0.1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

OpenSSL Project · OpenSSLversion=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

7.4CISA-ADPCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/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.

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-354Improper Validation of Integrity Check Value
T1556Modify Authentication Process

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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