CVE-2016-6870

CRITICAL

Out-of-bounds write in the (1) mb_detect_encoding, (2) mb_send_mail, and (3) mb_detect_order functions in Facebook HHVM before 3.15.0 allows attackers to have unspecified impact via unknown vectors.

Affects 1 product across 1 vendor.

CVSS 3.09.8
EPSS2.2%
Percentile82th
PatchUnknown
CVSS Vector — Plain English Remotely exploitable over the network, low complexity, no authentication required, no user interaction needed, impact contained to the vulnerable component, full confidentiality impact, full integrity impact, full availability impact.
CWE Weakness Definitions
CWE-787: Out-of-Bounds Write

Software writes data past buffer boundaries, corrupting memory and potentially enabling code execution.

◆ AI Analysis — automated analysis, not human-reviewed

This vulnerability was disclosed in 2017. A critical vulnerability affects Facebook systems (CVE-2016-6870). No public exploit code is currently available. Isolate affected systems if patching is not feasible.

BSID: BS-2017-GLOBAL-111998-C • Model: rule-based-v1 • Confidence: MEDIUM

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Frequently Asked Questions
What is CVE-2016-6870?
This vulnerability was disclosed in 2017. A critical vulnerability affects Facebook systems (CVE-2016-6870). No public exploit code is currently available. Isolate affected systems if patching is not feasible.
What is the CVSS score for CVE-2016-6870?
CVE-2016-6870 has CVSS 9.8 (Critical). Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H. EPSS: 2.2%.
Is CVE-2016-6870 actively exploited?
No confirmed active exploitation of CVE-2016-6870 as of 2026-09-25.
How do I remediate CVE-2016-6870?
Priority: MEDIUM. PSIRT: [email protected]
What systems are affected by CVE-2016-6870?
CVE-2016-6870 affects Facebook Hhvm.
Vulnerability Details
CVE IDCVE-2016-6870
BSIDBS-2017-GLOBAL-111998-C BreachSpider Global ID
CVSS VectorCVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Published2017-02-17
Last Modified2026-06-17
ICS Relevance15%
Weakness (CWE)
Out-of-Bounds Write
SourceNVD
Official Description

Out-of-bounds write in the (1) mb_detect_encoding, (2) mb_send_mail, and (3) mb_detect_order functions in Facebook HHVM before 3.15.0 allows attackers to have unspecified impact via unknown vectors.

Source: NIST NVD / MITRE CVE Database

Attack Vector Analysis — CITED Relevance

Vulnerability details: Out-of-bounds write in the (1) mb_detect_encoding, (2) mb_send_mail, and (3) mb_detect_order functions in Facebook HHVM before 3.15.0 allows attackers to have unspecified impact via unknown vectors. CVSS vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.

Exploitation Likelihood: LOW

Affected Products
VendorProductAffected Versions
Facebook Hhvm ≤ 3.14.5
Remediation

No official vendor advisory link on record. See the CVE record →

Vendor PSIRT: [email protected]
Threat Intelligence
● Threat Intelligence Validated: October 2026 | Threat Age: 3527 Days
CISA known-exploitedNot in KEV catalog
Public ExploitNot confirmed
PoC CodeNot confirmed
AI Enrichment Record — provenance & audit hash
Modelrule-based-v1
ConfidenceMEDIUM
Enriched At2026-05-24
SHA-512 Audit Hasha1da98ecdfba33b60e0b3d1fbe37e262eb00d33799698c5bd97deee7ea563bc048bbba8a3055a4f0b2842dfc999250532520fa8155dd7e5dd2783f14ce31c7a8
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