How severe is CVE-2019-11921?

CVE-2019-11921 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-2019-11921 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (79th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2019-11921?

CVE-2019-11921 affects Facebook Proxygen. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2019-11921?

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-2019-11921 published?

CVE-2019-11921 was published on 2019-07-25 and last updated on 2026-06-17.

CVE-2019-11921

CVE-2019-11921 is a critical-severity vulnerability in Facebook Proxygen 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-787.

Key facts

Severity: Critical (CVSS 3.x base score 9.8)
CVSS v2: 7.5
EPSS exploit prediction: 2% (79th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-787
Affected product: Facebook Proxygen
Published: 2019-07-25
Last modified: 2026-06-17

Description

An out of bounds write is possible via a specially crafted packet in certain configurations of Proxygen due to improper handling of Base64 when parsing malformed binary content in Structured HTTP Headers. This issue affects versions of proxygen prior to v2019.07.22.00.

Frequently asked questions

What is CVE-2019-11921?: An out of bounds write is possible via a specially crafted packet in certain configurations of Proxygen due to improper handling of Base64 when parsing malformed binary content in Structured HTTP Headers. This issue affects versions of proxygen prior to v2019.07.22.00.
How severe is CVE-2019-11921?: CVE-2019-11921 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-2019-11921 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (79th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2019-11921?: CVE-2019-11921 affects Facebook Proxygen. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2019-11921?: 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-2019-11921 published?: CVE-2019-11921 was published on 2019-07-25 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:facebook:proxygen:*:*:*:*:*:*:*:*

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