CVE-2026-63072
Analyzed
Analyzed - Analysis Complete
OpenSSL CMS Decryption Heap Out-of-Bounds Write
Vulnerability report for CVE-2026-63072, including description, CVSS score, EPSS score, affected products, exploitability, helpful resources, and attack-flow context.
Publication date: 2026-08-25
Last updated on: 2026-09-11
Assigner: OpenSSL Software Foundation
Description
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.
CVSS Scores
EPSS Scores
| Probability: | |
| Percentile: |
Meta Information
Affected Vendors & Products
| Vendor | Product | Version / Range |
|---|---|---|
| openssl | openssl | From 3.5.0 (inc) to 3.5.8 (exc) |
| openssl | openssl | From 3.6.0 (inc) to 3.6.4 (exc) |
| openssl | openssl | From 4.0.0 (inc) to 4.0.2 (exc) |
| openssl | openssl | From 3.4.0 (inc) to 3.4.7 (exc) |
| openssl | openssl | From 3.0.0 (inc) to 3.0.22 (exc) |
Helpful Resources
Exploitability
CWE
KEV
| CWE ID | Description |
|---|---|
| CWE-787 | The product writes data past the end, or before the beginning, of the intended buffer. |
