How severe is CVE-2018-6345?

CVE-2018-6345 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-2018-6345 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (75th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2018-6345?

CVE-2018-6345 affects Facebook Hhvm. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2018-6345?

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-2018-6345 published?

CVE-2018-6345 was published on 2019-01-15 and last updated on 2026-06-17.

CVE-2018-6345

CVE-2018-6345 is a critical-severity vulnerability in Facebook Hhvm 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% (75th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-787
Affected product: Facebook Hhvm
Published: 2019-01-15
Last modified: 2026-06-17

Description

The function number_format is vulnerable to a heap overflow issue when its second argument ($dec_points) is excessively large. The internal implementation of the function will cause a string to be created with an invalid length, which can then interact poorly with other functions. This affects all supported versions of HHVM (3.30.1 and 3.27.5 and below).

Frequently asked questions

What is CVE-2018-6345?: The function number_format is vulnerable to a heap overflow issue when its second argument ($dec_points) is excessively large. The internal implementation of the function will cause a string to be created with an invalid length, which can then interact poorly with other functions. This affects all supported versions of HHVM (3.30.1 and 3.27.5 and below).
How severe is CVE-2018-6345?: CVE-2018-6345 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-2018-6345 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (75th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2018-6345?: CVE-2018-6345 affects Facebook Hhvm. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2018-6345?: 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-2018-6345 published?: CVE-2018-6345 was published on 2019-01-15 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:facebook:hhvm:*:*:*:*:*:*:*:*

More vulnerabilities in Facebook Hhvm

CVE-2022-36937 — Critical (CVSS 9.8): HHVM 4.172.0 and all prior versions use TLS 1.0 for secure connections when handling tls:// URLs in the stream…
CVE-2021-24036 — Critical (CVSS 9.8): Passing an attacker controlled size when creating an IOBuf could cause integer overflow, leading to an out of bounds…
CVE-2020-1900 — Critical (CVSS 9.8): When unserializing an object with dynamic properties HHVM needs to pre-reserve the full size of the dynamic property…
CVE-2021-24025 — Critical (CVSS 9.8): Due to incorrect string size calculations inside the preg_quote function, a large input string passed to the function…
CVE-2020-1917 — Critical (CVSS 9.8): xbuf_format_converter, used as part of exif_read_data, was appending a terminating null character to the generated…
CVE-2020-1916 — Critical (CVSS 9.8): An incorrect size calculation in ldap_escape may lead to an integer overflow when overly long input is passed in,…

All CVEs affecting Facebook Hhvm →

Other CWE-787 (Out-of-bounds Write) vulnerabilities

CVE-2026-42369 — Critical (CVSS 10.0): GV-VMS V20 is a Video Monitoring Software used to gather the feeds of many surveillance cameras and manage other…
CVE-2026-4746 — Critical (CVSS 10.0): Out-of-bounds Write vulnerability in timeplus-io proton (base/poco/Foundation/src‎ modules). This vulnerability is…
CVE-2025-43300 — Critical (CVSS 10.0): An out-of-bounds write issue was addressed with improved bounds checking. This issue is fixed in iOS 15.8.5 and iPadOS…
CVE-2025-24201 — Critical (CVSS 10.0): An out-of-bounds write issue was addressed with improved checks to prevent unauthorized actions. This issue is fixed in…
CVE-2024-42479 — Critical (CVSS 10.0): llama.cpp provides LLM inference in C/C++. The unsafe `data` pointer member in the `rpc_tensor` structure can cause…
CVE-2024-39791 — Critical (CVSS 10.0): Stack-based buffer overflow vulnerabilities affecting Vonets industrial wifi bridge relays and wifi bridge…

Browse all CWE-787 (Out-of-bounds Write) vulnerabilities →