CVE-2026-63072

CVE-2026-63072 is a high-severity vulnerability in Openssl with a CVSS 3.x base score of 7.5. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-787.

Key facts

Description

Issue summary: OpenSSL CMS decryption sizes the key-unwrap output buffer based on querying the unwrapped key size, but the AES-WRAP-PAD unwrap primitive can write and cleanse more bytes than that query reports, causing an 8-byte out-of-bounds heap write. Impact summary: An attacker who supplies a crafted CMS message can trigger a deterministic 8-byte out-of-bounds heap write when the victim decrypts it with CMS_decrypt(), corrupting the heap and typically resulting in a Denial of Service. CWE: CWE-787: Out-of-bounds Write Description: The key-wrap OID is potentially attacker-controlled on the wire. CMS unwrapping allows both id-aesNNN-wrap-pad and id-aesNNN-wrap ciphers. An attacker can take a legitimate message and change a single OID byte to select the padded variant while leaving the message otherwise valid. Since the unwrap key is derived from the recipient's private operation (ECDH key agreement or ML-KEM decapsulation), the RFC 5649 integrity check cannot pass, and the decryption fails with integrity failure. The write is a fixed-size (8-byte), fixed-value (zero) heap overflow immediately past the allocation, requires no special configuration, and is reachable from the public CMS_decrypt() function. The consequence is a heap corruption leading to a Denial of Service. The fix in the CMS code sizes the unwrap output buffer for the worst case so a failed unwrap cannot write past the allocation. FIPS impact: no As the CMS code lives outside the FIPS module boundary, no FIPS modules are affected by this CVE.

Frequently asked questions

What is CVE-2026-63072?
Issue summary: OpenSSL CMS decryption sizes the key-unwrap output buffer based on querying the unwrapped key size, but the AES-WRAP-PAD unwrap primitive can write and cleanse more bytes than that query reports, causing an 8-byte out-of-bounds heap write. Impact summary: An attacker who supplies a crafted CMS message can trigger a deterministic 8-byte out-of-bounds heap write when the victim decrypts it with CMS_decrypt(), corrupting the heap and typically resulting in a Denial of Service. CWE: CWE-787: Out-of-bounds Write Description: The key-wrap OID is potentially attacker-controlled on the wire. CMS unwrapping allows both id-aesNNN-wrap-pad and id-aesNNN-wrap ciphers. An attacker can take a legitimate message and change a single OID byte to select the padded variant while leaving the message otherwise valid. Since the unwrap key is derived from the recipient's private operation (ECDH key agreement or ML-KEM decapsulation), the RFC 5649 integrity check cannot pass, and the decryption fails with integrity failure. The write is a fixed-size (8-byte), fixed-value (zero) heap overflow immediately past the allocation, requires no special configuration, and is reachable from the public CMS_decrypt() function. The consequence is a heap corruption leading to a Denial of Service. The fix in the CMS code sizes the unwrap output buffer for the worst case so a failed unwrap cannot write past the allocation. FIPS impact: no As the CMS code lives outside the FIPS module boundary, no FIPS modules are affected by this CVE.
How severe is CVE-2026-63072?
CVE-2026-63072 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.
Is CVE-2026-63072 being actively exploited?
It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (50th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-63072?
CVE-2026-63072 affects Openssl. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-63072?
Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
When was CVE-2026-63072 published?
CVE-2026-63072 was published on 2026-08-25 and last updated on 2026-09-11.

References

Affected products (1)

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Threat intelligence

Threat-intel indicators referencing this CVE: