nvd-client

Typed Python client for the National Vulnerability Database CVE and CPE Match APIs (version 2.0).

Documentation: https://ahur4.github.io/nvd-client/

The National Vulnerability Database is NIST's repository of publicly disclosed vulnerabilities. Each record is a CVE, with descriptions, references, CVSS scores, weaknesses, and the CPE configurations that say which products are affected. nvd-client calls the NVD REST API 2.0 and returns those documents as pydantic models.

Use it when a vulnerability scanner, asset inventory, or research notebook needs CVE or CPE match data and should not parse raw JSON by hand. It is a read-only client. It does not submit data to NVD.

Contents

• Documentation
• Installation
• Quickstart
• Configuration
• Rate limits and retries
• Return values
• Errors
• Migrating from 0.1.x
• Development
• Further reading

Installation

Python 3.10 or newer.

pip install nvd-client

HTTP and HTTPS proxies work with the base install. SOCKS proxies need the extra:

pip install "nvd-client[socks]"

From a checkout, including the linters and test runner:

pip install -e ".[dev]"

Quickstart

Pass an API key from the environment when you have one. The same calls work without a key; they then use NVD's public rate (see Rate limits and retries).

This program looks up one CVE, one page of CVEs published in the last seven days, and the CPE match strings for that CVE. Seven days is inside NVD's 120-day maximum. The datetimes are timezone-aware UTC.

import os
from datetime import datetime, timedelta, timezone

from nvd_client import NvdApi, NvdConfig

config = NvdConfig(
    api_key=os.environ.get("NVD_API_KEY"),
    results_per_page=100,
)
end = datetime.now(timezone.utc)
start = end - timedelta(days=7)

with NvdApi(config=config) as api:
    record = api.get_cve_by_id("CVE-2024-30078")
    print(record.id, record.vuln_status)
    print(record.description())
    print(record.cwe_ids)
    for metric in record.metrics.cvss_metric_v31:
        data = metric.cvss_data
        print(metric.type, data.base_score, data.vector_string)

    page = api.get_cve_by_date(
        publish_start_date=start,
        publish_end_date=end,
        per_page=50,
    )
    print(f"{len(page.cves)} of {page.total_results}")
    for cve in page.cves:
        print(cve.id, cve.published)

    found = api.get_cpes_by_cve("CVE-2024-30078", per_page=20)
    for item in found.matches:
        print(item.criteria, item.status, len(item.matches))

get_cve_by_id returns a CveRecord. A missing id raises NvdNotFoundError. get_cve_by_date returns one page, a CveListResponse: total_results is the size of the whole match, and cves is only this page. get_cpes_by_cve calls the CPE Match API (/cpematch/2.0) and returns a CpeMatchResponse. A page with total_results == 0 matched nothing. It is not an error.

get_cve_by_cpe goes the other way: CVEs whose applicability statement matches a CPE name. NVD requires a real part, vendor, product, and version in that name (* is not enough for those components). The same publish and modify date arguments are accepted.

from nvd_client import NvdApi

with NvdApi() as api:
    windows = api.get_cve_by_cpe(
        "cpe:2.3:o:microsoft:windows_10:1607:*:*:*:*:*:*:*",
        per_page=20,
    )

for cve in windows.cves:
    print(cve.id)

modify_start_date and modify_end_date filter on lastModified. A publish range and a modify range may be sent in one call. Each pair still has to be complete and no longer than 120 days.

To read past the first page, advance offset by the page size. There is no automatic pager.

import os
from datetime import datetime, timedelta, timezone

from nvd_client import NvdApi, NvdConfig

config = NvdConfig(api_key=os.environ.get("NVD_API_KEY"))
end = datetime.now(timezone.utc)
start = end - timedelta(days=7)
offset = 0

with NvdApi(config=config) as api:
    while True:
        page = api.get_cve_by_date(
            per_page=200,
            offset=offset,
            publish_start_date=start,
            publish_end_date=end,
        )
        for cve in page.cves:
            print(cve.id)
        offset = page.start_index + page.results_per_page
        if not page.cves or offset >= page.total_results:
            break

Dates

The client sends YYYY-MM-DDTHH:MM:SS.sss+00:00. requests percent-encodes the + as %2B, which is what NVD requires.

• An aware datetime, including one built with zoneinfo.ZoneInfo, is converted to UTC.
• A naive datetime is treated as UTC, not as the machine's local zone. datetime.now() is naive. Use datetime.now(timezone.utc).
• Named zones on Windows need the tzdata package. timezone.utc does not.
• One end without the other, an end before the start, or a span longer than 120 days raises InvalidParametersError before any request is sent.
• A non-datetime value raises InvalidDateFormatError.

Timestamps in NVD responses are parsed as datetime. Values without an offset stay naive. Values with Z or a numeric offset are aware.

Configuration

NvdConfig is frozen. Build a new config and a new client to change it. NvdApi(api_key) and NvdApi(api_key, proxy) still work. A non-None api_key or proxy argument overrides the same field on config. An empty or whitespace api_key is stored as None.

repr(client) reports whether a key is set. It does not include the key.

Field	Default	What it does
base_url	https://services.nvd.nist.gov/rest/json	CVE calls use {base_url}/cves/2.0. CPE match calls use {base_url}/cpematch/2.0. Must be http or https.
api_key	None	Sent as the apiKey header. Raises the NVD rate limit from 5 to 50 requests per 30 seconds.
timeout	30	Seconds, or a (connect, read) pair. Passed through to requests. Each part must be greater than 0.
results_per_page	2000	CVE page size when a call omits per_page. NVD's maximum is 2000.
cpe_results_per_page	500	CPE Match page size when a call omits per_page. NVD's maximum is 500.
rate_limit_delay	None	Seconds to wait between HTTP calls. None selects 6.0 without a key and 0.6 with one. 0 disables the wait.
max_retries	4	Extra attempts after the first request.
backoff_factor	1.0	Wait backoff_factor * 2**attempt seconds between retries, unless Retry-After is set.
max_backoff	60	Cap on that computed wait. A Retry-After value is not capped.
user_agent	nvd-client/<version> (+https://github.com/ahur4/nvd-client)	User-Agent header.
proxy	None	Used for both http and https. A proxy= argument on a single call replaces it for that call.

per_page=None on a method uses the config default. per_page outside 1..2000 (CVE) or 1..500 (CPE match), or a negative offset, raises InvalidParametersError.

Invalid config values raise ValueError when the config is constructed: a non-HTTP base URL, a non-positive timeout, a page size outside NVD's maximum, or a negative retry or backoff setting.

When proxy is left unset, requests still honors HTTP_PROXY and HTTPS_PROXY. A socks5:// or socks5h:// URL needs the socks extra.

import os

from nvd_client import NvdApi, NvdConfig

config = NvdConfig(
    api_key=os.environ.get("NVD_API_KEY"),
    timeout=(5.0, 60.0),
    results_per_page=100,
    user_agent="research-scanner/1.0",
)

with NvdApi(config=config) as api:
    page = api.get_all_cves()

Request a key from NIST: https://nvd.nist.gov/developers/request-an-api-key.

Use the client as a context manager, or call close(), so the connection pool is released. One client may be shared across threads. Calls take turns on the rate-limit clock.

Rate limits and retries

NVD's published windows, from the API start page:

Credential	Limit	Default delay
No API key	5 requests in a rolling 30 seconds	6.0 seconds
API key	50 requests in a rolling 30 seconds	0.6 seconds

The default delay is the window divided by the number of allowed requests, so a single client stays inside the limit. The first call does not wait. NIST also recommends sleeping for several seconds between requests so bursts are not rejected. Set rate_limit_delay=6 to do that even when a key is configured.

The client retries connection errors and HTTP 403, 429, 500, 502, 503, and 504. NVD uses 403 both for rate limits and for a rejected key. A 403 whose message says the API key is invalid is not retried. Any other 4xx, including 400 and 404, fails immediately.

With the defaults, a failure is followed by waits of 1, 2, 4, and 8 seconds (backoff_factor * 2**attempt), then the error is raised. max_backoff caps that series. If the response has Retry-After (a number of seconds or an HTTP date), that value replaces the computed wait.

After the retries are used up, a 403 or 429 raises NvdRateLimitError. Other exhausted failures raise NvdApiError.

Return values

Every successful call returns a pydantic model. Nothing returns a dict or None.

Method	Endpoint	Returns
get_all_cves(per_page=None, offset=0, proxy=None)	/cves/2.0	CveListResponse
get_cve_by_id(cve_id, proxy=None)	/cves/2.0	CveRecord
get_cve_by_date(...)	/cves/2.0	CveListResponse
get_cve_by_cpe(cpe_name, ...)	/cves/2.0	CveListResponse
get_cpes_by_cve(cve_id, ...)	/cpematch/2.0	CpeMatchResponse
get_cpes_by_criteria(criteria, ...)	/cpematch/2.0	CpeMatchResponse
get_cpes_by_criteria_name_id(criteria_name_id, ...)	/cpematch/2.0	CpeMatchResponse

get_cve_by_date and get_cve_by_cpe also take per_page, offset, publish_start_date, publish_end_date, modify_start_date, modify_end_date, and proxy. The CPE match methods take per_page, offset, and proxy.

Serialization

Attributes are snake_case. The NVD names are aliases, so both forms validate.

record.model_dump()
record.model_dump(by_alias=True)
record.model_dump(by_alias=True, mode="json", exclude_none=True)
record.model_dump_json(by_alias=True, indent=2)

model_dump() uses Python names (last_modified) and leaves datetime objects in place. by_alias=True uses the NVD names (lastModified). mode="json" and model_dump_json() render datetimes as ISO strings.

Unknown JSON keys are kept (extra="allow") and show up in model_dump(). A field NVD adds later does not drop the rest of the document and is not discarded. Metric groups that NVD omits are empty lists, not None.

CveListResponse

Attribute	NVD name	Meaning
results_per_page	resultsPerPage	Records in this response
start_index	startIndex	Offset NVD used
total_results	totalResults	Size of the full match
format	format	Response format name
version	version	API version string
timestamp	timestamp	When NVD generated the page
vulnerabilities	vulnerabilities	CveItem wrappers
cves		CveRecord objects on this page

CveRecord

description(lang="en") returns that language's text, or None. cwe_ids is the weakness description values (CWE-787, NVD-CWE-noinfo, and similar).

Attribute	NVD name	Notes
id	id	CVE-YYYY-NNNN
source_identifier	sourceIdentifier
vuln_status	vulnStatus
published	published	datetime
last_modified	lastModified	datetime
descriptions	descriptions	LangString (lang, value)
references	references	url, optional source and tags
metrics	metrics	CVSS v2, v3.0, v3.1, v4.0, and SSVC
weaknesses	weaknesses	Weakness: source, type, description
configurations	configurations	CPE applicability tree
affected	affected	Affected: source, affected_data
cve_tags	cveTags	CveTag: source_identifier, tags
vendor_comments	vendorComments	organization, comment, last_modified
evaluator_comment	evaluatorComment
evaluator_solution	evaluatorSolution
evaluator_impact	evaluatorImpact
cisa_exploit_add	cisaExploitAdd	date, when the CVE is in the KEV catalog
cisa_action_due	cisaActionDue	date
cisa_required_action	cisaRequiredAction
cisa_vulnerability_name	cisaVulnerabilityName

Metrics holds cvss_metric_v2, cvss_metric_v30, cvss_metric_v31, cvss_metric_v40, and ssvc_v203. Each CVSS metric has source, type (Primary or Secondary), and cvss_data (version, vector_string, base_score, plus that version's base metrics). v2, v3.0, and v3.1 wrappers also carry exploitability_score and impact_score when NVD sends them. v2 adds base_severity and the privilege flags. v4 scores that NVD attaches to the vector (threat, environmental) live on cvss_data.

A configuration node (ConfigNode) has operator, negate, and cpe_match. Each CpeMatch has vulnerable, criteria, match_criteria_id, and the optional version bounds. AffectedProduct carries vendor, product, versions, and the other product fields from the NVD affected schema.

The full field list is nvd_client.models.

CpeMatchResponse

Attribute	NVD name	Meaning
results_per_page	resultsPerPage	Match strings in this response
start_index	startIndex	Offset NVD used
total_results	totalResults	Size of the full match
format	format
version	version
timestamp	timestamp
match_strings	matchStrings	Wrappers around CpeMatchString
matches		The CpeMatchString objects on this page

CpeMatchString has criteria, match_criteria_id, created, last_modified, status, optional version bounds, cpe_last_modified, and matches (CpeNameMatch: cpe_name, cpe_name_id).

Errors

NvdClientError
├── InvalidDateFormatError
├── InvalidParametersError
├── InvalidCVEIDError
├── NvdApiError
│   ├── NvdRateLimitError
│   └── NvdNotFoundError
└── NvdResponseError

Exception	When it is raised
InvalidCVEIDError	The id is not CVE-YYYY-NNNN with at least four digits in the sequence. No request is sent.
InvalidDateFormatError	A date argument is not a datetime.
InvalidParametersError	A date range is incomplete, reversed, or longer than 120 days. per_page or offset is out of range. A required CPE name, criteria, or match-criteria id is blank.
ValueError	NvdConfig itself is invalid (base URL, timeout, page-size bounds, negative retry settings).
NvdNotFoundError	HTTP 404, or get_cve_by_id received an empty page. An empty id lookup is still HTTP 200, so status_code is 200. Subclass of NvdApiError.
NvdRateLimitError	HTTP 403 or 429 after retries. Subclass of NvdApiError.
NvdApiError	Any other HTTP error, including a rejected API key, and connection or timeout failures after retries.
NvdResponseError	The body was not JSON, or it did not match the pydantic model.

NvdApiError (and its subclasses) expose status_code and url. status_code is None when the failure happened before a response, for example a timeout.

from nvd_client import NvdApi, NvdNotFoundError, NvdRateLimitError

with NvdApi() as api:
    try:
        record = api.get_cve_by_id("CVE-2024-30078")
    except NvdNotFoundError as exc:
        print(exc.status_code, exc)
    except NvdRateLimitError:
        raise

Migrating from 0.1.x

0.2.0 changes the return types and stops hiding failed requests. The method names are the same.

# 0.1.x returned a dict, or None when the request failed.
raw = api.get_cve_by_id("CVE-2024-30078")
if raw is None:
    ...
else:
    cve_id = raw["vulnerabilities"][0]["cve"]["id"]

# 0.2.0 returns a CveRecord and raises when the CVE is missing.
from nvd_client import NvdNotFoundError

try:
    record = api.get_cve_by_id("CVE-2024-30078")
except NvdNotFoundError:
    ...
else:
    cve_id = record.id
    document = record.model_dump(by_alias=True, mode="json")

Collection calls (get_all_cves, get_cve_by_date, get_cve_by_cpe) return CveListResponse. Read page.cves, not page["vulnerabilities"]. CPE match calls return CpeMatchResponse.

Other breaks:

• Python 3.10 or newer is required.
• Failures raise the exceptions in Errors. Check total_results for an empty match. Do not check for None.
• Date arguments must be datetime values. Strings are rejected. Naive values are UTC. Ranges longer than 120 days are rejected locally.
• pytz is not a dependency. The old import existed so the package could build an unused Asia/Tehran zone, and a fresh pip install failed because pytz was never declared in install_requires.
• per_page above NVD's maximum raises InvalidParametersError.
• A proxy passed to one call overrides the client proxy. In 0.1.x the client proxy won and the argument was ignored.
• str(client) describes the base URL and whether a key is set.
• model_dump() is the replacement for treating the response as a dictionary. Pass by_alias=True when you need NVD's camelCase keys.

See CHANGELOG.md for the dependency changes that went with this release.

Development

pip install -e ".[dev]"
ruff check .
ruff format --check .
mypy --strict nvd_client
pytest

Documentation site:

pip install -e ".[docs]"
mkdocs build --strict
mkdocs serve

Tests mock HTTP. They do not call NVD. GitHub Actions runs the same checks on Python 3.10 through 3.14, and runs mkdocs build --strict on pull requests. Pushes to main publish the site to GitHub Pages.

Further reading

• Documentation
• NVD API quick start, including the rate limits
• CVE API
• CPE and CPE Match APIs
• Request an API key
• Changelog
• MIT license

Maintained by Ahur4.