NULL pointer dereference in OpenSSL
CVE-2026-42766
Issue summary: A specially crafted password-encrypted CMS message can trigger a NULL pointer dereference during CMS decryption. Impact summary: This NULL pointer dereference leads to an application crash and a Denial of Service. The CMS PasswordRecipientInfo.keyDerivationAlgorithm field is defined as OPTIONAL in the ASN.1 specification and may therefore be absent in specially crafted inputs. During the password-based CMS decryption the OpenSSL CMS implementation dereferences this field without first checking whether it was present. An attacker who supplies such a CMS message to an application performing password-based CMS decryption can trigger an application crash, leading to a Denial of Service. Applications that process password-encrypted CMS messages may be affected. The FIPS modules in 4.0, 3.6, 3.5, 3.4, and 3.0 are not affected by this issue, as the affected code is outside the OpenSSL FIPS module boundary.
Published · last modified .
CVSS v3 metric
CVSS v3 base score 5.9 (Medium). Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H.
EPSS exploit prediction
EPSS: 0.011 (64.6th percentile), scored .
Low probability of exploitation in the next 30 days, but still tracked. 65th percentile — 64.6% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.011 · newest: 0.011 · change: +0.001
Affected products
- OpenSSL — versions 4.0.0, 3.6.0, 3.5.0
Weakness classification (CWE)
References
- github.com/openssl/security/commit/056d06c1918fafbb98c1c85a02e4c47cc4e199ce
- github.com/openssl/security/commit/12bc26ffb3a2be728c9b86e1cae277de5b33dfa4
- github.com/openssl/security/commit/3ff64913615d648cfbb6a6f1cf5529ae7ea829d7
- github.com/openssl/security/commit/ab52d88cb5374876d59aee3c91f9e4ccce2b7ce4
- github.com/openssl/security/commit/da26f368732b83e40e9d356fe61c3d3aaab6d2e8
- openssl-library.org/news/secadv/20260609.txt (vendor-advisory, Vendor Advisory)
- github.com/openssl/openssl/commit/056d06c1918fafbb98c1c85a02e4c47cc4e199ce (Patch, patch)
- github.com/openssl/openssl/commit/12bc26ffb3a2be728c9b86e1cae277de5b33dfa4 (Patch, patch)
- github.com/openssl/openssl/commit/3ff64913615d648cfbb6a6f1cf5529ae7ea829d7 (Patch, patch)
- github.com/openssl/openssl/commit/ab52d88cb5374876d59aee3c91f9e4ccce2b7ce4 (Patch, patch)
Frequently asked questions
- What is CVE-2026-42766?
- CVE-2026-42766 is a medium-severity vulnerability in OpenSSL, classified under NULL Pointer Dereference. CVSS score: 5.9/10. Published 2026-06-09.
- How severe is CVE-2026-42766?
- Medium severity. CVSS v3 base score is 5.9 out of 10.