CVE-2026-34181: PKCS#12 Files with PBMAC1 Are Accepted with Short HMAC Keys
- Is it exploited?
Not on CISA's list. CISA has not added it to the Known Exploited Vulnerabilities catalog as of . If CISA adds it, this page shows it as known exploited.
- How likely is exploitation in the next 30 days?
- 0.4%
Up from 0.2% on .
EPSS score, percentile 31.6 of all scored records. A probability estimated by FIRST, not a report of exploitation.
- How severe?
- 7.4 High
CVSS v3.1 base score, from CISA's enrichment of the record
- What should I do?
CISA has set no required action, because the vulnerability is not in KEV.
- Which versions are affected?
Affected
- from 4.0.0 to before 4.0.1
- from 3.6.0 to before 3.6.3
- from 3.5.0 to before 3.5.7
- from 3.4.0 to before 3.4.6
Source: CISA KEV 2026.10.29, as of ; FIRST EPSS, as of ; CVE List, as of . About the data.
What to do
Advisories and patches
This summary is based on the CVE record as of . Check the vendor's advisory before you act: affected versions and fixes can change.
Affected products and versions
As listed in the CVE record.
| Status | Versions |
|---|---|
| Affected | from 4.0.0 to before 4.0.1 |
| Affected | from 3.6.0 to before 3.6.3 |
| Affected | from 3.5.0 to before 3.5.7 |
| Affected | from 3.4.0 to before 3.4.6 |
Versions not listed are: unaffected.
Source: CVE List, as of . About the data.
About this vulnerability
Issue Summary: The PKCS#12 file processing fails to perform sufficient input validation for files that use Password-Based Message Authentication Code 1 (PBMAC1) integrity mechanism allowing a certificate and private key forgery. Impact Summary: An attacker impersonating a user can cause a service reading PKCS#12 files to accept forged certificates and private keys with a 1 in 256 probability. I…
Summary: CVE record, as of .
- CISA has not added CVE-2026-34181 to its Known Exploited Vulnerabilities (KEV) catalog, as of 29 Oct 2026.
- The CVE record was published on 9 Jun 2026.
- The CVE record carries a CVSS v3.1 base score of 7.4 (High), taken from CISA's enrichment of the record.
- FIRST's EPSS model puts the probability of exploitation in the next 30 days at 0.4% (percentile 31.6), as of 29 Oct 2026. EPSS is a statistical estimate, not a report of exploitation.
- CISA's SSVC assessment in the CVE record: exploitation none, automatable no, technical impact partial.
- The credits in the CVE record name Anthropic (Claude) as finder.
Source: CISA KEV 2026.10.29, as of ; CVE List, as of ; FIRST EPSS, as of . About the data.
Description
PKCS#12 Files with PBMAC1 Are Accepted with Short HMAC Keys
Issue Summary: The PKCS#12 file processing fails to perform sufficient input validation for files that use Password-Based Message Authentication Code 1 (PBMAC1) integrity mechanism allowing a certificate and private key forgery. Impact Summary: An attacker impersonating a user can cause a service reading PKCS#12 files to accept forged certificates and private keys with a 1 in 256 probability. If a service accepting PKCS#12 files is using passwords for authenticating the received files, the attacker can create unencrypted PKCS#12 files that use PBMAC1 authentication that specifies an HMAC key of only one byte, allowing them to craft a file that will be accepted with a 1 in 256 probability. That would then cause the service to accept a certificate and private key controlled by the attacker. The FIPS modules are not affected by this issue, as the affected code is outside the OpenSSL FIPS module boundary.
Source: CVE List, as of . About the data.
Weakness
CWE-354
- CWE-354: Improper Validation of Integrity Check Value
CWE and CAPEC are maintained by MITRE; the entries are those named in the CVE record.
Timeline
| Date | Event |
|---|---|
| CVE record published | |
| CVE record last updated |
Known exploited OpenSSL vulnerabilities
- CVE-2014-0160: OpenSSL Information Disclosure Vulnerability