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CVE-2019-3557

30
FAUCET Score

CVE-2019-3557 is a critical out-of-bounds read vulnerability affecting all supported versions of HHVM (3.30 and 3.27.4 and below). It stems from improperly implemented readImpl functions in bz2 and php://output streams, leading to an out-of-bounds read when certain stream functions are used. With a CVSS score of 9.8 (CRITICAL), this vulnerability is remotely exploitable with low attack complexity, potentially leading to high impact on confidentiality, integrity, and availability. There is currently no evidence of active exploitation, public exploit code, or significant community discussion surrounding this CVE.

Impacted Technologies

VendorProductVersion(s)CPE
<= 3.27.4CPE matchmatch criteria
cpe:2.3:a:facebook:hhvm:*:*:*:*:*:*:*:*
>= 3.28.0, <= 3.30.0CPE matchmatch criteria
cpe:2.3:a:facebook:hhvm:*:*:*:*:*:*:*:*
< 3.27.5CPE match
cpe:2.3:a:facebook:hhvm:*:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.0

9.8CRITICAL

CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
HIGH
Integrity Impact
HIGH
Availability Impact
HIGH
Exploitability Score
3.9
Impact Score
5.9
CvssVersion
3.0

Exploit Intelligence

EPSS Score
1.71%
Probability of exploitation in next 30 days
EPSS Percentile
75.0%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.0171 is in the 63rd percentile among its peer group of 36,897 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.1 Reddit, 0.3 Bluesky, 0.3 Mastodon, and 2.4 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.3 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Patch Available

Vendor Patches (1)

github_advisorypatch availablevia nvd_reference
View patch

References

github.com / facebook/hhvm/commit/6e4dd9ec3f14b48170fc45dc9d13a3261765f994
PatchThird Party Advisory
hhvm.com / blog/2019/01/14/hhvm-3.30.2.html
Vendor Advisory