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CVE-2026-69247— cryptography: PKCS#7 EnvelopedData decryption exposes a Bleichenbacher oracle through distinguishable errors and timing

Quick assessment

Affected
pyca cryptography
Exploitation
Public or AI PoC available; prioritize validation
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Python Cryptographic Authority cryptography是Python Cryptographic Authority组织开源的一款密码学工具库。 Python Cryptographic Authority cryptography 44.0.0版本至50.0.0之前版本存在安全漏洞，该漏洞源于pkcs7_decrypt_der、pkcs7_decrypt_pem和pkcs7_decrypt_smime函数在解密过程中对RSA填充错误处理不当，导致攻击者可通过响应差异或时序

CVSS 8.2 · High EPSS 0.27% · P18

Possible ATT&CK Techniques 1 AI

T1555 · Credentials from Password Stores

Affected Version Matrix 1

VendorProduct Version RangeStatus
pyca cryptography >= 44.0.0, < 50.0.0 affected
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I. Basic Information for CVE-2026-69247

Vulnerability Information
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Vulnerability Title
cryptography: PKCS#7 EnvelopedData decryption exposes a Bleichenbacher oracle through distinguishable errors and timing
Source: CVE Program / CVE List V5
Vulnerability Description
cryptography is a package designed to expose cryptographic primitives and recipes to Python developers. From 44.0.0 until 50.0.0, pkcs7_decrypt_der, pkcs7_decrypt_pem, and pkcs7_decrypt_smime reported the outcome of decrypting a RecipientInfo's encryptedKey in several distinguishable ways, one of which disclosed the exact length recovered from the RSA operation. The same distinction was also observable by timing. An application that decrypts attacker-supplied EnvelopedData and reflects the outcome gives the attacker a Bleichenbacher oracle against the content-encryption key. Decryption ran as RSA PKCS#1 v1.5 decrypt of encryptedKey, build an AES cipher from the result, then AES-CBC decrypt and PKCS#7 unpad. Invalid RSA padding, a valid padding with a bad key length, a correct length with a wrong key, and the real key each failed or succeeded differently. Case 1 is reachable only where the linked library lacks implicit rejection: OpenSSL 3.0 and 3.1, LibreSSL, and BoringSSL. Exploitation requires a service that auto-decrypts untrusted EnvelopedData matching the victim certificate and answers adaptively at high volume, such as an S/MIME gateway or mail filter. This issue is fixed in 50.0.0.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N
Source: CVE Program / CVE List V5
Vulnerability Type
通过时间差异性导致的信息暴露
Source: CVE Program / CVE List V5
Vulnerability Title
Python Cryptographic Authority cryptography 信息泄露漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Python Cryptographic Authority cryptography是Python Cryptographic Authority组织开源的一款密码学工具库。 Python Cryptographic Authority cryptography 44.0.0版本至50.0.0之前版本存在安全漏洞，该漏洞源于pkcs7_decrypt_der、pkcs7_decrypt_pem和pkcs7_decrypt_smime函数在解密过程中对RSA填充错误处理不当，导致攻击者可通过响应差异或时序
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
pyca cryptography >= 44.0.0, < 50.0.0 -

II. Public POCs for CVE-2026-69247

# POC Description Source Link Shenlong Link
AI-Generated POC Verified env Premium
Qwen3.6-35B-A3B · 13209 chars
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III. Intelligence Information for CVE-2026-69247

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Patches & Fixes for CVE-2026-69247 (2)

Vendor Advisories for CVE-2026-69247 (1)

Same Patch Batch · pyca · 2026-08-03 · 3 CVEs total

CVE-2026-69249 8.7 HIGH python-cryptography: Duplicate self-signed intermediates can cause exponential path-buildi
CVE-2026-69248 6.9 MEDIUM python-cryptography verifier accepts wildcard DNS names allowing escape from permittedSubt

IV. Related Vulnerabilities

Same product: cryptography
Same vendor: pyca
Same weakness: CWE-208

V. Comments for CVE-2026-69247

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