What is CVE-2019-3561?

CVE-2019-3561 is a critical-severity vulnerability in Facebook Hhvm, classified under Improper Restriction of Operations within the Bounds of a Memory Buffer. CVSS score: 9.8/10. Published 2019-04-29.

How severe is CVE-2019-3561?

Critical severity. CVSS v3 base score is 9.8 out of 10.

Buffer overflow in Facebook Hhvm

CVE-2019-3561

Insufficient boundary checks for the strrpos and strripos functions allow access to out-of-bounds memory. This affects all supported versions of HHVM (4.0.3, 3.30.4, and 3.27.7 and below).

Vulnerability class: Buffer Overflow

Published 2019-04-29 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 9.8 (Critical). Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.

EPSS exploit prediction

EPSS: 0.017 (77.0th percentile), scored 2026-10-19.

Low probability of exploitation in the next 30 days, but still tracked. 77th percentile — 77.0% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.017 · newest: 0.017 · change: 0.000

Affected products

Facebook Hhvm — versions 4.0.4, 4.0.0, 3.30.5

Weakness classification (CWE)

References

github.com/facebook/hhvm/commit/46003b4ab564b2abcd8470035fc324fe36aa8c75 (Third Party Advisory)
hhvm.com/blog/2019/04/03/hhvm-4.0.4.html (Vendor Advisory)

Frequently asked questions

What is CVE-2019-3561?: CVE-2019-3561 is a critical-severity vulnerability in Facebook Hhvm, classified under Improper Restriction of Operations within the Bounds of a Memory Buffer. CVSS score: 9.8/10. Published 2019-04-29.
How severe is CVE-2019-3561?: Critical severity. CVSS v3 base score is 9.8 out of 10.