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CVE-2026-63072— Heap Buffer Overflow in CMS Key Unwrapping

Quick assessment

Affected
OpenSSL OpenSSL
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

OpenSSL是OpenSSL团队开源的一个提供安全通信加密功能的软件库。 OpenSSL 4.0.0版本至4.0.2之前版本、3.6.0版本至3.6.4之前版本、3.5.0版本至3.5.8之前版本、3.4.0版本至3.4.7之前版本、3.0.0版本至3.0.22之前版本和1.1.1版本至1.1.1zi之前版本存在缓冲区错误漏洞，该漏洞源于CMS解密时输出缓冲区大小计算不当，导致越界堆写入，可能造成堆损坏和拒绝服务。

AI Predicted 7.5 Difficulty: Easy EPSS 0.92% · P60

Possible ATT&CK Techniques 1 AI

T1496 · Resource Hijacking

Affected Version Matrix 6

VendorProduct Version RangeStatus
OpenSSL OpenSSL 4.0.0< 4.0.2 affected
3.6.0< 3.6.4 affected
3.5.0< 3.5.8 affected
3.4.0< 3.4.7 affected
3.0.0< 3.0.22 affected
1.1.1< 1.1.1zi affected
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I. Basic Information for CVE-2026-63072

Vulnerability Information
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Vulnerability Title
Heap Buffer Overflow in CMS Key Unwrapping
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
N/A
Source: CVE Program / CVE List V5
Vulnerability Type
跨界内存写
Source: CVE Program / CVE List V5
Vulnerability Title
OpenSSL 缓冲区错误漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
OpenSSL是OpenSSL团队开源的一个提供安全通信加密功能的软件库。 OpenSSL 4.0.0版本至4.0.2之前版本、3.6.0版本至3.6.4之前版本、3.5.0版本至3.5.8之前版本、3.4.0版本至3.4.7之前版本、3.0.0版本至3.0.22之前版本和1.1.1版本至1.1.1zi之前版本存在缓冲区错误漏洞，该漏洞源于CMS解密时输出缓冲区大小计算不当，导致越界堆写入，可能造成堆损坏和拒绝服务。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
OpenSSL OpenSSL 4.0.0 ~ 4.0.2 -

II. Public POCs for CVE-2026-63072

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III. Intelligence Information for CVE-2026-63072

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Patches & Fixes for CVE-2026-63072 (5)

Vendor Advisories for CVE-2026-63072 (1)

Same Patch Batch · OpenSSL · 2026-08-25 · 9 CVEs total

CVE-2026-75803 AEAD Forgeries with Empty Ciphertext When Using EVP_Cipher()
CVE-2026-18798 QUIC Server May Trigger Double Free When Processing INITIAL Packet
CVE-2026-54874 Excessive Memory Use Buffering DTLS Records for a Future Epoch
CVE-2026-63074 CMP Indefinite Cache Growth of ExtraCerts
CVE-2026-63073 Untrusted Sender DN Used as Format String in CMP Response Validation
CVE-2026-63075 QUIC ACK-only Packet Retention Can Cause Memory Exhaustion
CVE-2026-63076 Invalid Pointer Dereference in CMP Server via Crafted protectionAlg
CVE-2026-14457 RPK Server Signature Algorithm Selection Can Dereference a Missing Certificate

IV. Related Vulnerabilities

Same product: OpenSSL
Same vendor: OpenSSL
Same weakness: CWE-787

V. Comments for CVE-2026-63072

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