How severe is CVE-2018-1000656?

CVE-2018-1000656 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.

Is CVE-2018-1000656 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 4% (90th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2018-1000656?

CVE-2018-1000656 primarily affects Palletsprojects Flask. In total, 4 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2018-1000656?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

When was CVE-2018-1000656 published?

CVE-2018-1000656 was published on 2018-08-20 and last updated on 2026-06-17.

CVE-2018-1000656

CVE-2018-1000656 is a high-severity vulnerability in Palletsprojects Flask with a CVSS 3.x base score of 7.5. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-20.

Key facts

Severity: High (CVSS 3.x base score 7.5)
CVSS v2: 5.0
EPSS exploit prediction: 4% (90th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-20
Affected product: Palletsprojects Flask
Published: 2018-08-20
Last modified: 2026-06-17

Description

The Pallets Project flask version Before 0.12.3 contains a CWE-20: Improper Input Validation vulnerability in flask that can result in Large amount of memory usage possibly leading to denial of service. This attack appear to be exploitable via Attacker provides JSON data in incorrect encoding. This vulnerability appears to have been fixed in 0.12.3. NOTE: this may overlap CVE-2019-1010083.

Frequently asked questions

What is CVE-2018-1000656?: The Pallets Project flask version Before 0.12.3 contains a CWE-20: Improper Input Validation vulnerability in flask that can result in Large amount of memory usage possibly leading to denial of service. This attack appear to be exploitable via Attacker provides JSON data in incorrect encoding. This vulnerability appears to have been fixed in 0.12.3. NOTE: this may overlap CVE-2019-1010083.
How severe is CVE-2018-1000656?: CVE-2018-1000656 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.
Is CVE-2018-1000656 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 4% (90th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2018-1000656?: CVE-2018-1000656 primarily affects Palletsprojects Flask. In total, 4 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2018-1000656?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
When was CVE-2018-1000656 published?: CVE-2018-1000656 was published on 2018-08-20 and last updated on 2026-06-17.

References

Affected products (4)

cpe:2.3:a:palletsprojects:flask:*:*:*:*:*:*:*:*
cpe:2.3:a:netapp:active_iq:*:*:*:*:*:*:*:*
cpe:2.3:a:netapp:hyper_converged_infrastructure:*:*:*:*:*:*:*:*
cpe:2.3:a:netapp:ontap_select_deploy_utility:*:*:*:*:*:*:*:*

More vulnerabilities in Palletsprojects Flask

CVE-2023-30861 — High (CVSS 7.5): Flask is a lightweight WSGI web application framework. When all of the following conditions are met, a response…
CVE-2019-1010083 — High (CVSS 7.5): The Pallets Project Flask before 1.0 is affected by: unexpected memory usage. The impact is: denial of service. The…
CVE-2026-27205 — Medium (CVSS 4.3): Flask is a web server gateway interface (WSGI) web application framework. In versions 3.1.2 and below, when the session…

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Threat intelligence

Threat-intel indicators referencing this CVE:

210.211.19.178 (ipv4-addr)
8.215.3.250 (ipv4-addr)