Application crash via unchecked stream-cipher key length
Published Jun 9, 2026 · Updated Jun 9, 2026
Out-of-bounds read in OpenSSL CMS password-based decryption allows remote attackers to crash applications processing untrusted CMS data. kek_unwrap_key() accepts an attacker-selected stream-mode KEK cipher, applies an ineffective block-length guard, and reads seven check bytes from a shorter heap allocation. No password is required, but a crash requires the allocation to border an unmapped page; the excess bytes are not disclosed, and FIPS modules are unaffected.
Summary
What happened
Out-of-bounds read in OpenSSL CMS password-based decryption allows remote attackers to crash applications processing untrusted CMS data. kek_unwrap_key() accepts an attacker-selected stream-mode KEK cipher, applies an ineffective block-length guard, and reads seven check bytes from a shorter heap allocation. No password is required, but a crash requires the allocation to border an unmapped page; the excess bytes are not disclosed, and FIPS modules are unaffected.
The record
- CVE
- CVE-2026-9076
- Published
- Jun 9, 2026
- Updated
- Jun 9, 2026
- Vendor
- OpenSSL Project
- Product
- OpenSSL
- Classifications
- CWE-125, CAPEC-540, T1499.004
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Jun 9, 2026CVE publishedPublication date reported by the CVE source.
- 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.
- Affected versionversion=1.0.2 <1.0.2zq
- Affected versionversion=1.1.1 <1.1.1zh
- Affected versionversion=3.0.0 <3.0.21
- Affected versionversion=3.4.0 <3.4.6
- Affected versionversion=3.5.0 <3.5.7
- Affected versionversion=3.6.0 <3.6.3
- Affected versionversion=4.0.0 <4.0.1
What conditions does exploitation require?
What is affected?
Published CVSS scores
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.
Weakness, pattern, technique
Public exploit references
- CMS PWRI short-key reproducerproof of concept · demonstrated
Labels summarize the accepted research assessment. They do not indicate a test against your environment.
Technologies
Your stack
See the directory against your own environment.
Your stack
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