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CVE-2026-34180— Heap Buffer Over-read in ASN.1 Content Parsing

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团队的一个开源的能够实现安全套接层（SSLv2/v3）和安全传输层（TLSv1）协议的通用加密库。该产品支持多种加密算法，包括对称密码、哈希算法、安全散列算法等。 OpenSSL存在缓冲区错误漏洞，该漏洞源于ASN.1解码器中整数截断问题，当原始元素内容长度超过2GB时，可能导致堆缓冲区过度读取，在64位Unix及类Unix平台上可能造成应用崩溃或解码出输入缓冲区之外的内存内容。

AI Predicted 5.5 Difficulty: Moderate EPSS 1.31% · P70

Possible ATT&CK Techniques 1 AI

T1190 · Exploit Public-Facing Application

Affected Version Matrix 7

VendorProduct Version RangeStatus
OpenSSL OpenSSL 4.0.0< 4.0.1 affected
3.6.0< 3.6.3 affected
3.5.0< 3.5.7 affected
3.4.0< 3.4.6 affected
3.0.0< 3.0.21 affected
1.1.1< 1.1.1zh affected
1.0.2< 1.0.2zq affected
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I. Basic Information for CVE-2026-34180

Vulnerability Information
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Vulnerability Title
Heap Buffer Over-read in ASN.1 Content Parsing
Source: CVE Program / CVE List V5
Vulnerability Description
Issue summary: Parsing a crafted DER-encoded ASN.1 structure with a primitive element whose content exceeds 2 gigabytes in length may cause a heap buffer over-read on 64-bit Unix and Unix-like platforms. Impact summary: The heap buffer over-read may crash the application (Denial of Service) or to load into the decoded ASN.1 object contents of memory beyond the end of the input buffer. More typically such ASN.1 elements would instead be truncated. An integer truncation in OpenSSL's ASN.1 decoder causes the content length of an ASN.1 primitive element to be mishandled when it exceeds 2 gigabytes. In the worst case the truncated length is treated as a request to scan the binary content for a terminating zero byte, possibly causing OpenSSL to read either less than or beyond the end of the allocated buffer. Applications that pass attacker-supplied data to d2i_X509(), d2i_PKCS7(), or any other d2i_* decoding function are affected. OpenSSL's own command-line tools are not vulnerable, as data read through the BIO layer is checked before it reaches the affected code. The issue only affects 64-bit Unix and Unix-like platforms; 32-bit platforms and 64-bit Windows are not affected. The FIPS modules in 4.0, 3.6, 3.5, 3.4 and 3.0 are not affected by this issue, as the affected code is outside the OpenSSL FIPS module boundary.
Source: CVE Program / CVE List V5
CVSS Information
N/A
Source: CVE Program / CVE List V5
Vulnerability Type
跨界内存读
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团队的一个开源的能够实现安全套接层（SSLv2/v3）和安全传输层（TLSv1）协议的通用加密库。该产品支持多种加密算法，包括对称密码、哈希算法、安全散列算法等。 OpenSSL存在缓冲区错误漏洞，该漏洞源于ASN.1解码器中整数截断问题，当原始元素内容长度超过2GB时，可能导致堆缓冲区过度读取，在64位Unix及类Unix平台上可能造成应用崩溃或解码出输入缓冲区之外的内存内容。
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 ~ 4.0.1 -

II. Public POCs for CVE-2026-34180

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III. Intelligence Information for CVE-2026-34180

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Patches & Fixes for CVE-2026-34180 (5)

Vendor Advisories for CVE-2026-34180 (1)

Same Patch Batch · OpenSSL · 2026-06-09 · 18 CVEs total

CVE-2026-45447 Heap Use-After-Free in the PKCS7_verify() Function
CVE-2026-34183 Unbounded Memory Growth in the QUIC PATH_CHALLENGE Handler
CVE-2026-34181 PKCS#12 Files with PBMAC1 Are Accepted with Short HMAC Keys
CVE-2026-34182 CMS AuthEnvelopedData Processing May Accept Forged Messages
CVE-2026-9076 Out-of-Bounds Read in CMS Password-Based Decryption
CVE-2026-35188 Double-free When Checking OCSP Stapled Response
CVE-2026-7383 Possible Heap Buffer Overflow in ASN.1 Multibyte String Conversion
CVE-2026-45446 Incorrect Tag Processing for Empty Messages in AES-GCM-SIV and AES-SIV modes
CVE-2026-45445 AES-OCB IV Ignored on EVP_Cipher() Path
CVE-2026-42771 Possible Out of Bounds Read in X509_VERIFY_PARAM_set1_email()
CVE-2026-42768 Multi-RecipientInfo Bleichenbacher Oracle in CMS_decrypt() and PKCS7_decrypt()
CVE-2026-42769 Trust-Anchor Substitution via cert/issuer Typo in CMP rootCaKeyUpdate
CVE-2026-42767 NULL Pointer Dereference in CRMF EncryptedValue Decryption
CVE-2026-42766 Possible NULL Dereference in Password-Based CMS Decryption
CVE-2026-42764 NULL Pointer Dereference in QUIC Server Initial Packet Handling
CVE-2026-42770 FFC-DH Peer Validation Uses Attacker-Supplied q
CVE-2026-42765 NULL Dereference in Certificate Verification with OCSP Checking

IV. Related Vulnerabilities

Same product: OpenSSL
Same vendor: OpenSSL
Same weakness: CWE-125

V. Comments for CVE-2026-34180

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