Is CVE-2019-3557 actively exploited?

No active exploitation of CVE-2019-3557 has been confirmed so far. Continue monitoring, as exploit status can change.

Can CVE-2019-3557 be exploited remotely?

Yes. CVE-2019-3557 is exploitable remotely over the network (CVSS attack vector: Network).

What is the CVSS score of CVE-2019-3557?

CVE-2019-3557 has a CVSS score of 9.8 (CRITICAL).

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CRITICAL

CVE-2019-3557

CWE-125Published: January 15, 2019· Updated: Jun 17, 2026

9.8

CVSS v3.1

Official Description

The implementations of streams for bz2 and php://output improperly implemented their readImpl functions, returning -1 consistently. This behavior caused some stream functions, such as stream_get_line, to trigger an out-of-bounds read when operating on such malformed streams. The implementations were updated to return valid values consistently. This affects all supported versions of HHVM (3.30 and 3.27.4 and below).

NVD Source

Technical Analysis

CVE-2019-3557 can be exploited remotely over the network without requiring physical or adjacent access, significantly expanding the attack surface for threat actors.

The vulnerability requires no privileges and no user interaction, making it a prime target for automated exploitation campaigns and worm-like propagation.

A successful exploit results in complete confidentiality breach (data exposure), full integrity compromise (data manipulation), availability disruption (denial of service), with a CVSS base score of 9.8.