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CVE-2026-31789— Heap Buffer Overflow in Hexadecimal Conversion

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存在安全漏洞，该漏洞源于将过大的OCTET STRING值转换为十六进制字符串时导致堆缓冲区溢出，可能导致崩溃或攻击者控制代码执行。

AI Predicted 3.7 Difficulty: Hard EPSS 0.33% · P23

Possible ATT&CK Techniques 1 AI

T1203 · Exploitation for Client Execution

Affected Version Matrix 5

VendorProduct Version RangeStatus
OpenSSL OpenSSL 3.6.0< 3.6.2 affected
3.5.0< 3.5.6 affected
3.4.0< 3.4.5 affected
3.3.0< 3.3.7 affected
3.0.0< 3.0.20 affected
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I. Basic Information for CVE-2026-31789

Vulnerability Information
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Vulnerability Title
Heap Buffer Overflow in Hexadecimal Conversion
Source: CVE Program / CVE List V5
Vulnerability Description
Issue summary: Converting an excessively large OCTET STRING value to a hexadecimal string leads to a heap buffer overflow on 32 bit platforms. Impact summary: A heap buffer overflow may lead to a crash or possibly an attacker controlled code execution or other undefined behavior. If an attacker can supply a crafted X.509 certificate with an excessively large OCTET STRING value in extensions such as the Subject Key Identifier (SKID) or Authority Key Identifier (AKID) which are being converted to hex, the size of the buffer needed for the result is calculated as multiplication of the input length by 3. On 32 bit platforms, this multiplication may overflow resulting in the allocation of a smaller buffer and a heap buffer overflow. Applications and services that print or log contents of untrusted X.509 certificates are vulnerable to this issue. As the certificates would have to have sizes of over 1 Gigabyte, printing or logging such certificates is a fairly unlikely operation and only 32 bit platforms are affected, this issue was assigned Low severity. The FIPS modules in 3.6, 3.5, 3.4, 3.3 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
跨界内存写
Source: CVE Program / CVE List V5
Vulnerability Title
OpenSSL 安全漏洞
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存在安全漏洞，该漏洞源于将过大的OCTET STRING值转换为十六进制字符串时导致堆缓冲区溢出，可能导致崩溃或攻击者控制代码执行。
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 3.6.0 ~ 3.6.2 -

II. Public POCs for CVE-2026-31789

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III. Intelligence Information for CVE-2026-31789

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Patches & Fixes for CVE-2026-31789 (5)

Vendor Advisories for CVE-2026-31789 (1)

Same Patch Batch · OpenSSL · 2026-04-07 · 7 CVEs total

CVE-2026-31790 Incorrect Failure Handling in RSA KEM RSASVE Encapsulation
CVE-2026-28388 NULL Pointer Dereference When Processing a Delta CRL
CVE-2026-28387 Potential Use-after-free in DANE Client Code
CVE-2026-28386 Out-of-bounds Read in AES-CFB-128 on X86-64 with AVX-512 Support
CVE-2026-28390 Possible NULL Dereference When Processing CMS KeyTransportRecipientInfo
CVE-2026-28389 Possible NULL Dereference When Processing CMS KeyAgreeRecipientInfo

IV. Related Vulnerabilities

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

V. Comments for CVE-2026-31789

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