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CVE-2026-45271— picotls has infinite recursion in the minicrypto ASN.1 decoder

Quick assessment

Affected
h2o picotls
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.

Picotls 是一个 TLS 协议库，允许用户根据其用例选择不同的密码学后端。Picotls 实现了自己的 ASN.1 验证辅助函数，该函数在 minicrypto 后端解析本地 PKCS#8 私钥时被使用。在提交 c14231d801407640bc42c2dcf92783409ea6a7c7 之前，该验证器在递归深入构造型 ASN.1 元素时，未强制实施最大嵌套深度限制。如果应用程序通过 ptls_minicrypto_load_private_key() 加载攻击者提供的私钥文件，或者对不受信任的 DER

CVSS 5.5 · Medium EPSS 0.11% · P2

Possible ATT&CK Techniques 1 AI

T1190 · Exploit Public-Facing Application

Affected Version Matrix 1

VendorProduct Version RangeStatus
h2o picotls < c14231d801407640bc42c2dcf92783409ea6a7c7 affected
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I. Basic Information for CVE-2026-45271

Vulnerability Information
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Vulnerability Title
picotls has infinite recursion in the minicrypto ASN.1 decoder
Source: CVE Program / CVE List V5
Vulnerability Description
Picotls is a TLS protocol library that allows users select different crypto backends based on their use case. Picotls implements its own ASN.1 validation helper, which is used by the minicrypto backend while parsing local PKCS#8 private keys. Prior to commit c14231d801407640bc42c2dcf92783409ea6a7c7, the validator recursively descends into constructed ASN.1 elements without enforcing a maximum nesting depth. If an application loads an attacker-supplied private-key file through ptls_minicrypto_load_private_key(), or otherwise calls the public ASN.1 validation API on untrusted DER, a crafted deeply nested ASN.1 structure can exhaust the process stack and crash the application. Note that the libcrypto (OpenSSL) backend does not use the ASN.1 validation helper of picotls, and therefore is immune to this vulnerability. The vulnerability has been addressed in commit c14231d801407640bc42c2dcf92783409ea6a7c7.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
不可达退出条件的循环(无限循环)
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
h2o picotls < c14231d801407640bc42c2dcf92783409ea6a7c7 -

II. Public POCs for CVE-2026-45271

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III. Intelligence Information for CVE-2026-45271

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Patches & Fixes for CVE-2026-45271 (1)

Vendor Advisories for CVE-2026-45271 (1)

IV. Related Vulnerabilities

Same product: picotls
Same vendor: h2o
Same weakness: CWE-835

V. Comments for CVE-2026-45271

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