Heap Buffer Overflow in CMS Key Unwrapping

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-63072
StatePUBLISHED
Assigneropenssl
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-08-25 13:19:26 UTC
Updated2026-09-11 21:16:34 UTC
DescriptionIssue 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.

Risk And Classification

Primary CVSS: v3.1 7.5 HIGH from ADP

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS: 0.006120000 probability, percentile 0.468620000 (date 2026-08-30)

Problem Types: CWE-787 | CWE-787 CWE-787 Out-of-bounds Write

VersionSourceTypeScoreSeverityVector
3.1ADPDECLARED7.5HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
3.1134c704f-9b21-4f2e-91b3-4a467353bcc0Secondary7.5HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

NVD Known Affected Configurations (CPE 2.3)

TypeVendorProductVersionUpdateEditionLanguage
Application Openssl Openssl All All All All

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA OpenSSL OpenSSL affected 4.0.0 4.0.2 semver Not specified
CNA OpenSSL OpenSSL affected 3.6.0 3.6.4 semver Not specified
CNA OpenSSL OpenSSL affected 3.5.0 3.5.8 semver Not specified
CNA OpenSSL OpenSSL affected 3.4.0 3.4.7 semver Not specified
CNA OpenSSL OpenSSL affected 3.0.0 3.0.22 semver Not specified
CNA OpenSSL OpenSSL affected 1.1.1 1.1.1zi custom Not specified

References

ReferenceSourceLinkTags
github.com/openssl/openssl/commit/9ec2f6d2ae2bcad907cf7ee38584855bafe4979a [email protected] github.com Patch
openssl-library.org/news/secadv/20260825.txt [email protected] openssl-library.org Vendor Advisory
github.com/openssl/openssl/commit/9530a5fd1aacaeccdced4478ea2340a480613335 [email protected] github.com Patch
github.com/openssl/openssl/commit/87784ad619af36b8807c2044b3940006fccc1e42 [email protected] github.com Patch
github.com/openssl/openssl/commit/a0c8ec557d9cac078f032d76cdf684fe743eb382 [email protected] github.com Patch
github.com/openssl/openssl/commit/2a3dac874c8057c1f0186849bf1ede1ae7b6b756 [email protected] github.com Patch
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis

Vendor Comments And Credit

Discovery Credit

CNA: Bhabani Sankar Das (en)

CNA: Filipe Casal(Trail of Bits) (en)

CNA: Daniel Kubec (en)

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