Pyca Cryptography: Observable Timing Discrepancy (CVE-2026-69247)
Published Last modified Sources: Red Hat, BSI, Ubuntu, OSV, CVE.org, SUSE
What is affected, what to do
A flaw was found in cryptography, a Python package for cryptographic primitives. This vulnerability, known as a Bleichenbacher oracle, arises during PKCS#7 EnvelopedData decryption.
The available sources name no fixed version. Check the vendor guidance in the references below.
- Affected
- Pyca Cryptography
gte 44.0.0, < 50.0.0..*
- Pyca Cryptography
Not sure whether and how you are affected? Ask a question about this vulnerability
Metrics
8.2
Priority
XIEM Effective CVSS: highest available CVSS rating from NVD and vendor data.
Source: NVD, CVSS v4
8.2
CVSS v4
Severity High on the scale from 0 to 10.
Source: Red Hat, BSI, Ubuntu, OSV, CVE.org, SUSE
0.3 %
EPSS score
Low — model estimates < 1% exploitation likelihood.
Source: FIRST EPSS, percentile 18.7
Show all metrics
- Severity
- High
Priority (0–325)
The priority score is a consolidated metric that condenses several individual signals into a single, action-guiding ranking: technical severity (CVSS), exploitation likelihood (EPSS), known-exploited status (KEV) and the context of the affected asset. The aim is to answer the only truly important question in vulnerability management: what first?
Read in glossary- 66.86 Methodology
Exploit maturity
An exploit is code or a technique that specifically uses a concrete vulnerability to force unintended behaviour — such as executing code or escalating privileges. It is the tool that turns a theoretical flaw into a practical attack.
Read in glossary- no public PoC known
XIEM Effective CVSS
XIEM® is the tiered managed-security operating model from NEOSEC and a registered trademark of NEOSEC GmbH. It extends classic SIEM — the central collection, normalisation and correlation of security-relevant events — with endpoint forensics, network visibility and deception technology, and consolidates them into three building tiers: Sentry, Orchestrate and Command.
Read in glossary- 8.2 Methodology
CVSS v4
CVSS is the globally established, open standard for assessing the technical severity of a vulnerability on a scale from 0 to 10. It describes how easily a flaw can be exploited and what damage it can cause — but not how likely its actual exploitation is. CVSS and the complementary EPSS deliberately answer different questions.
Read in glossary- 8.2
EPSS score
The EPSS score is the absolute model output for an individual vulnerability: the estimated probability of real-world exploitation within the next 30 days, expressed as a value between 0 and 1 (i.e. 0 % to 100 %). A score of 0.42 means „the model estimates a 42 % chance of real-world exploitation within 30 days“.
Read in glossary- 0.3 %
- Low — model estimates < 1% exploitation likelihood.
EPSS percentile
The EPSS percentile is the relative position of a vulnerability within all EPSS-scored CVEs, expressed as a value between 0 and 1. A percentile of 0.90 means „this CVE has a higher EPSS score than 90 % of all other scored CVEs“. Unlike the EPSS score, it is not a probability — but a positioning within a ranking.
Read in glossary- 18.7
- Elevated — this CVE ranks above at least 10% of all CVEs scored today.
KEV status
The KEV catalogue is a list maintained by the US authority CISA of vulnerabilities for which active exploitation in the wild has been confirmed. It answers not the question „how severe?“ but „is it already being attacked?“ — thereby sharply prioritising patching.
Read in glossary- —
- Published
CWE
CWE is a catalogue of typical weakness types in software and hardware — such as flawed input validation, unsafe memory handling or poor authentication. Where a CVE names a concrete vulnerability in a concrete product, a CWE describes the underlying class of defect.
Read in glossary- CWE-208, CWE-209
Detection rules
No NEOSEC detection rule is available for this vulnerability yet.
Classification under NIS2 and CRA
Rule-based classification from exploitation status and severity. It does not replace a case-by-case assessment.
NIS2
NIS2 is EU Directive (EU) 2022/2555 to raise the level of cybersecurity across the Union. It substantially broadens obligations compared with the first NIS directive: more sectors, mandatory risk management, staged reporting duties and personal accountability of senior management.
Read in glossary- High technical severity: assess and remediate the vulnerability in vulnerability handling under Art. 21(2)(e) NIS2 and document the decision.
CRA
The CRA is EU Regulation (EU) 2024/2847 setting horizontal cybersecurity requirements for „products with digital elements“ — from industrial controllers and software to connected consumer devices. For the first time manufacturers must ensure security across the entire product lifecycle, handle vulnerabilities and provide security updates.
Read in glossary- From 11.12.2027, Annex I Part II CRA requires manufacturers of affected products with digital elements to handle vulnerabilities without delay and provide security updates.
ISO/IEC 27001
ISO/IEC 27001 is the internationally leading standard for an information security management system (ISMS). It describes a risk-based, process-oriented framework to systematically plan, implement, review and improve information security.
Read in glossary- Control A.8.8, management of technical vulnerabilities: assess relevance to your systems, plan remediation and keep evidence.
Description
A flaw was found in cryptography, a Python package for cryptographic primitives. This vulnerability, known as a Bleichenbacher oracle, arises during PKCS#7 EnvelopedData decryption. An attacker can exploit distinguishable error messages and timing differences during decryption to gain information about the content-encryption key. Exploitation requires a high-volume service, such as an S/MIME gateway, that automatically decrypts untrusted data matching a victim's certificate. Successful exploitation could lead to the disclosure of sensitive encryption keys, allowing an attacker to decrypt confidential communications.
Source: redhat_csaf, BSI CSAF, BSI WID Portal, Ubuntu Security Notices, OSV (Open Source Vulnerabilities), NVD (NIST), cvelistv5, CVE.org (MITRE), suse_csaf
Affected products
The following versions are affected. Older releases of the same product line are also vulnerable unless stated otherwise.
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| pyca | cryptography |
|
|
| Oracle | Communications |
|
|
Affected operating systems
| Family | Vendor | Product | Version |
|---|---|---|---|
| Linux | ubuntu | python-cryptography | bionic |
| Linux | ubuntu | python-cryptography | resolute |
Weakness classes (CWE)
CWE-208Observable Timing Discrepancy
Base
Two separate operations in a product require different amounts of time to complete, in a way that is observable to an actor and reveals security-relevant information about the state of the product, such as whether a particular operation was successful or not.
Entry at MITRE CWE-208CWE-209Generation of Error Message Containing Sensitive Information
Base
The product generates an error message that includes sensitive information about its environment, users, or associated data.
Entry at MITRE CWE-209
References & sources
- github.compyca/cryptography/security/advisories/GHSA-g6cj-pr64-35w5web, x_refsource_CONFIRM
- github.compyca/cryptography/pull/15369web, x_refsource_MISC
- github.compyca/cryptography/commit/53fccd93413a8d7f07d6d8999681f27b75cffa…web, x_refsource_MISC
- github.compyca/cryptographypackage
- pypi.orgproject/cryptographypackage
- GitHub Security Advisoriesadvisories/GHSA-g6cj-pr64-35w5advisory
- NVD (NIST)vuln/detail/CVE-2026-69247advisory
Reanalysis & status changes
Chronological NVD audit events for this CVE — reanalyses, CVSS updates, CPE diffs.
CVE Modified134c704f-9b21-4f2e-91b3-4a467353bcc0
- SSVC: after {"id":"CVE-2026-69247","role":"CISA Coordinator","options":[{"exploitation":"none"},{"automatable":"no"},{"technicalI…
New CVE Receivedsecurity-advisories@github.com
- Affected: after cryptography
- Description: after 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.
- CVSS V4.0: after AV:N/AC:H/AT:P/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
- CWE: after CWE-208
Embed badge
Show the severity and KEV status of this vulnerability on your site – with a link back here. The image is updated hourly.
<a href="https://intel.neosec.eu/en/cve/CVE-2026-69247"><img src="https://intel.neosec.eu/badge/cve/CVE-2026-69247.svg?lang=en" alt="CVE-2026-69247 – NEOSEC Intel" height="20"></a>