How severe is CVE-2020-1911?

CVE-2020-1911 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2020-1911 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (78th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2020-1911?

CVE-2020-1911 affects Facebook Hermes. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2020-1911?

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

When was CVE-2020-1911 published?

CVE-2020-1911 was published on 2020-09-04 and last updated on 2026-06-17.

CVE-2020-1911

CVE-2020-1911 is a critical-severity vulnerability in Facebook Hermes with a CVSS 3.x base score of 9.8. 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-843.

Key facts

Severity: Critical (CVSS 3.x base score 9.8)
CVSS v2: 6.8
EPSS exploit prediction: 2% (78th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-843
Affected product: Facebook Hermes
Published: 2020-09-04
Last modified: 2026-06-17

Description

A type confusion vulnerability when resolving properties of JavaScript objects with specially-crafted prototype chains in Facebook Hermes prior to commit fe52854cdf6725c2eaa9e125995da76e6ceb27da allows attackers to potentially execute arbitrary code via crafted JavaScript. Note that this is only exploitable if the application using Hermes permits evaluation of untrusted JavaScript. Hence, most React Native applications are not affected.

Frequently asked questions

What is CVE-2020-1911?: A type confusion vulnerability when resolving properties of JavaScript objects with specially-crafted prototype chains in Facebook Hermes prior to commit fe52854cdf6725c2eaa9e125995da76e6ceb27da allows attackers to potentially execute arbitrary code via crafted JavaScript. Note that this is only exploitable if the application using Hermes permits evaluation of untrusted JavaScript. Hence, most React Native applications are not affected.
How severe is CVE-2020-1911?: CVE-2020-1911 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2020-1911 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (78th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2020-1911?: CVE-2020-1911 affects Facebook Hermes. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2020-1911?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.
When was CVE-2020-1911 published?: CVE-2020-1911 was published on 2020-09-04 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:facebook:hermes:*:*:*:*:*:*:*:*

More vulnerabilities in Facebook Hermes

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CVE-2023-23556 — Critical (CVSS 9.8): An error in BigInt conversion to Number in Hermes prior to commit a6dcafe6ded8e61658b40f5699878cd19a481f80 could have…
CVE-2022-40138 — Critical (CVSS 9.8): An integer conversion error in Hermes bytecode generation, prior to commit 6aa825e480d48127b480b08d13adf70033237097,…

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Other CWE-843 vulnerabilities

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CVE-2023-22579 — Critical (CVSS 9.9): Due to improper parameter filtering in the sequalize js library, can a attacker peform injection.
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CVE-2026-43038 — Critical (CVSS 9.8): In the Linux kernel, the following vulnerability has been resolved: ipv6: icmp: clear skb2->cb[] in…
CVE-2025-70023 — Critical (CVSS 9.8): An issue pertaining to CWE-843: Access of Resource Using Incompatible Type was discovered in transloadit uppy v0.25.6.

Browse all CWE-843 vulnerabilities →