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.
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.
Metrics
Affected Vendors & Products
No data.
No data.
OpenCVE Enrichment is a feature of OpenCVE that uses AI to automatically link vendors and products to CVEs. Learn more on GitHub.
| Vendors | Products |
|---|---|
|
Openssl
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|
Openssl
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Advisories
| Source | ID | Title |
|---|---|---|
 Debian DSA |
DSA-6465-1 | openssl security update |
 Ubuntu USN |
USN-8678-1 | OpenSSL vulnerabilities |
Fixes
Solution
No solution given by the vendor.
Workaround
No workaround given by the vendor.
References
History
Tue, 25 Aug 2026 15:30:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Metrics |
cvssV3_1
|
Tue, 25 Aug 2026 15:00:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| First Time appeared |
Openssl
Openssl openssl |
|
| Vendors & Products |
Openssl
Openssl openssl |
Tue, 25 Aug 2026 13:15:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| 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. | |
| Title | Heap Buffer Overflow in CMS Key Unwrapping | |
| Weaknesses | CWE-787 | |
| References |
|
|
Projects
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MITRE
Status: PUBLISHED
Assigner: openssl
Published:
Updated: 2026-08-25T14:29:55.378Z
Reserved: 2026-07-15T13:10:26.188Z
Link: CVE-2026-63072
Vulnrichment
Updated: 2026-08-25T14:29:44.760Z
NVD
Status : Received
Published: 2026-08-25T13:19:26.010
Modified: 2026-08-25T15:16:36.060
Link: CVE-2026-63072
Redhat
No data.
OpenCVE Enrichment
Updated: 2026-08-25T17:00:04Z
Weaknesses