CVE-2026-63072 (GCVE-0-2026-63072)
Vulnerability from cvelistv5 – Published: 2026-08-25 12:59 – Updated: 2026-08-25 14:29
VLAI
EPSS
VEX
Title
Heap Buffer Overflow in CMS Key Unwrapping
Summary
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.
Severity
7.5 (High)
SSVC
Exploitation: none
Automatable: yes
Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-08-25 14:29 UTC
CWE
- CWE-787 - Out-of-bounds Write
Assigner
References
6 references
Impacted products
Date Public
2026-08-25 11:36
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"value": "Issue summary: OpenSSL CMS decryption sizes the key-unwrap output buffer based\u003cbr\u003eon querying the unwrapped key size, but the AES-WRAP-PAD unwrap primitive\u003cbr\u003ecan write and cleanse more bytes than that query reports, causing an 8-byte\u003cbr\u003eout-of-bounds heap write.\u003cbr\u003e\u003cbr\u003eImpact summary: An attacker who supplies a crafted CMS message can trigger a\u003cbr\u003edeterministic 8-byte out-of-bounds heap write when the victim decrypts it\u003cbr\u003ewith CMS_decrypt(), corrupting the heap and typically resulting in a Denial\u003cbr\u003eof Service.\u003cbr\u003e\u003cbr\u003eCWE: CWE-787: Out-of-bounds Write\u003cbr\u003e\u003cbr\u003eDescription: The key-wrap OID is potentially attacker-controlled on the wire.\u003cbr\u003eCMS unwrapping allows both id-aesNNN-wrap-pad and id-aesNNN-wrap ciphers.\u003cbr\u003eAn attacker can take a legitimate message and change a single OID byte to\u003cbr\u003eselect the padded variant while leaving the message otherwise valid. Since\u003cbr\u003ethe unwrap key is derived from the recipient\u0027s private operation (ECDH key\u003cbr\u003eagreement or ML-KEM decapsulation), the RFC 5649 integrity check cannot\u003cbr\u003epass, and the decryption fails with integrity failure.\u003cbr\u003e\u003cbr\u003eThe write is a fixed-size (8-byte), fixed-value (zero) heap overflow\u003cbr\u003eimmediately past the allocation, requires no special configuration, and is\u003cbr\u003ereachable from the public CMS_decrypt() function. The consequence is\u003cbr\u003ea heap corruption leading to a Denial of Service. The fix in the CMS code\u003cbr\u003esizes the unwrap output buffer for the worst case so a failed unwrap cannot\u003cbr\u003ewrite past the allocation.\u003cbr\u003e\u003cbr\u003eFIPS impact: no\u003cbr\u003e\u003cbr\u003eAs the CMS code lives outside the FIPS module boundary, no FIPS\u003cbr\u003emodules are affected by this CVE."
}
],
"value": "Issue summary: OpenSSL CMS decryption sizes the key-unwrap output buffer based\non querying the unwrapped key size, but the AES-WRAP-PAD unwrap primitive\ncan write and cleanse more bytes than that query reports, causing an 8-byte\nout-of-bounds heap write.\n\nImpact summary: An attacker who supplies a crafted CMS message can trigger a\ndeterministic 8-byte out-of-bounds heap write when the victim decrypts it\nwith CMS_decrypt(), corrupting the heap and typically resulting in a Denial\nof Service.\n\nCWE: CWE-787: Out-of-bounds Write\n\nDescription: The key-wrap OID is potentially attacker-controlled on the wire.\nCMS unwrapping allows both id-aesNNN-wrap-pad and id-aesNNN-wrap ciphers.\nAn attacker can take a legitimate message and change a single OID byte to\nselect the padded variant while leaving the message otherwise valid. Since\nthe unwrap key is derived from the recipient\u0027s private operation (ECDH key\nagreement or ML-KEM decapsulation), the RFC 5649 integrity check cannot\npass, and the decryption fails with integrity failure.\n\nThe write is a fixed-size (8-byte), fixed-value (zero) heap overflow\nimmediately past the allocation, requires no special configuration, and is\nreachable from the public CMS_decrypt() function. The consequence is\na heap corruption leading to a Denial of Service. The fix in the CMS code\nsizes the unwrap output buffer for the worst case so a failed unwrap cannot\nwrite past the allocation.\n\nFIPS impact: no\n\nAs the CMS code lives outside the FIPS module boundary, no FIPS\nmodules are affected by this CVE."
}
],
"metrics": [
{
"format": "other",
"other": {
"content": {
"text": "Moderate"
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"type": "https://openssl-library.org/policies/general/security-policy/"
}
}
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"cweId": "CWE-787",
"description": "CWE-787 Out-of-bounds Write",
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"type": "CWE"
}
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}
],
"providerMetadata": {
"dateUpdated": "2026-08-25T12:59:34.428Z",
"orgId": "3a12439a-ef3a-4c79-92e6-6081a721f1e5",
"shortName": "openssl"
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"references": [
{
"name": "OpenSSL Advisory",
"tags": [
"vendor-advisory"
],
"url": "https://openssl-library.org/news/secadv/20260825.txt"
},
{
"name": "4.0.2 git commit",
"tags": [
"patch"
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"url": "https://github.com/openssl/openssl/commit/9530a5fd1aacaeccdced4478ea2340a480613335"
},
{
"name": "3.6.4 git commit",
"tags": [
"patch"
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"url": "https://github.com/openssl/openssl/commit/2a3dac874c8057c1f0186849bf1ede1ae7b6b756"
},
{
"name": "3.5.8 git commit",
"tags": [
"patch"
],
"url": "https://github.com/openssl/openssl/commit/87784ad619af36b8807c2044b3940006fccc1e42"
},
{
"name": "3.4.7 git commit",
"tags": [
"patch"
],
"url": "https://github.com/openssl/openssl/commit/9ec2f6d2ae2bcad907cf7ee38584855bafe4979a"
},
{
"name": "3.0.22 git commit",
"tags": [
"patch"
],
"url": "https://github.com/openssl/openssl/commit/a0c8ec557d9cac078f032d76cdf684fe743eb382"
}
],
"source": {
"discovery": "UNKNOWN"
},
"title": "Heap Buffer Overflow in CMS Key Unwrapping",
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}
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"cveMetadata": {
"assignerOrgId": "3a12439a-ef3a-4c79-92e6-6081a721f1e5",
"assignerShortName": "openssl",
"cveId": "CVE-2026-63072",
"datePublished": "2026-08-25T12:59:34.428Z",
"dateReserved": "2026-07-15T13:10:26.188Z",
"dateUpdated": "2026-08-25T14:29:55.378Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2"
}
}
}
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Experimental. This forecast is provided for visualization only and may change without notice. Do not use it for operational decisions.
Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
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The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the
vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base
model, served locally by ML-Gateway.
They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
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Related by attack behaviour
Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.
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