HKDF in cryptography before 1.5.2 returns an empty byte-string if used with a length less than algorithm.digest_size.
- Published
- Mar 27, 2017
- Updated
- Jun 16, 2026
- EPSS
- 3.5% · 89th percentile
- CWE
- —
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Report tools
Action score
31
Monitor
Low priority for now.
- CVSS
- 30 / 40 · 7.5 / 10
- CISA KEV
- 0 / 30 · Not listed
- EPSS
- 1 / 30 · 3.5%
Affected systems
| Vendor | Product | CPE |
|---|---|---|
| cryptography.io | cryptography | cpe:2.3:a:cryptography.io:cryptography |
| fedoraproject | fedora | cpe:2.3:o:fedoraproject:fedora |
| canonical | ubuntu linux | cpe:2.3:o:canonical:ubuntu_linux |
Affected versions
NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.
- canonical ubuntu linux16.04
- canonical ubuntu linux16.10
- cryptography.io cryptographyup to 1.5.2 inclusive
- fedoraproject fedora23
- fedoraproject fedora24
- fedoraproject fedora25
Package-level exposure
OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.
| Ecosystem | Package | Affected range | Fix |
|---|---|---|---|
| Debian:12 | python-cryptography | before 1.5.3-1 | 1.5.3-1 |
| PyPI | cryptography | before 1.5.3 | 1.5.3 |
Same product
cryptography.io: all recordsOther highest-scoring records for the same primary product.
- CVE-2020-36242In the cryptography package before 3.3.2 for Python, certain sequences of update calls to symmetrically encrypt multi-GB values could result38Monitor
- CVE-2026-26007cryptography Subgroup Attack Due to Missing Subgroup Validation for SECT Curves32Monitor
- CVE-2024-26130cryptography NULL pointer deference with pkcs12.serialize_key_and_certificates when called with a non-matching certificate and private key and an hmac_hash over30Monitor
- CVE-2023-49083cryptography vulnerable to NULL-dereference when loading PKCS7 certificates30Monitor
- CVE-2023-38325The cryptography package before 41.0.2 for Python mishandles SSH certificates that have critical options.30Monitor
- CVE-2026-39892cryptography has a buffer overflow if non-contiguous buffers were passed to APIs27Monitor
Remediation
Which version to upgrade to
Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.
| Product / package | Fixed version | Source |
|---|---|---|
| debian:python-cryptography | 1.5.3-1 · Debian:12 | Package registry (OSV) |
| PyPI:cryptography | 1.5.3 | Package registry (OSV) |
Exploit status
No known public exploit
No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.
Research context
For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.
Timeline
From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.
No dated events beyond publication.
FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).
Patch and commit links
Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.
Credits
All researchersFinders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.
No credits in the CNA record.
Variant candidates
Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.
No nightly-computed relations.
Chain candidates
An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.
—
Bug bounty scope
No known public program.
Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).
Technical details
Attack conditions
- Anyone who can reach it over the internet can trigger it.
- No account or password is required.
- No user action is required.
- No special conditions are required; it is repeatable.
If successful
- Confidentiality
- none
- Integrity
- high · data or configuration can be modified
- Availability
- none
- Attack vector
- Network
- Attack complexity
- Low
- Privileges required
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality impact
- None
- Integrity impact
- High
- Availability impact
- None
Weakness class (CWE)
—
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
nvd-primary
Attack context
MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.
MITRE has no CAPEC/ATT&CK mapping for this CWE.
Noroxi analysis
No Noroxi analysis for this record yet
We don't hand-write analysis for all 385,000+ vulnerabilities; that wouldn't be honest. For notable, high-impact vulnerabilities our team writes the mechanism, detection and remediation steps.
We use this product, ask for helpChange log
- Fix✗ → ✓
For records you follow, these changes also arrive as notifications. →
References
- www.openwall.com/lists/oss-security/2016/11/09/2
- www.securityfocus.com/bid/94216
- www.ubuntu.com/usn/USN-3138-1
- cryptography.io/en/latest/changelog
- github.com/pyca/cryptography/commit/b924696b2e8731f39696584d12cceeb3aeb2d874
- github.com/pyca/cryptography/issues/3211
- lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/5R2ZOBMPWDFFHUZ6QOZZY36A6H5CGJXL/
- lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/U23KDR2M2N7W2ZSREG63BVW7D4VC6CIZ/
- lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/WQ5G7KHKZC4SI23JE7277KZXM57GEQKT/
Vendor advisories and official records. Exploit/PoC links are deliberately left out.