CVE-2023-5176Network attack vector

Arbitrary code execution

Published Sep 27, 2023 · Updated May 1, 2025

Memory corruption in Firefox before 118, Firefox ESR before 115.3, and Thunderbird before 115.3 allows attackers to run arbitrary code. Mozilla grouped eight memory-safety defects under this CVE but has not publicly identified their affected components or unsafe operations. The browser products expose the risk in browser-like content; Thunderbird generally blocks email exploitation because scripting is disabled while mail is read.

CVSS severity9.8
Critical
EPSS probability1.24%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Memory corruption in Firefox before 118, Firefox ESR before 115.3, and Thunderbird before 115.3 allows attackers to run arbitrary code. Mozilla grouped eight memory-safety defects under this CVE but has not publicly identified their affected components or unsafe operations. The browser products expose the risk in browser-like content; Thunderbird generally blocks email exploitation because scripting is disabled while mail is read.

The record

CVE
CVE-2023-5176
Published
Sep 27, 2023
Updated
May 1, 2025
Vendor
Mozilla
Product
Firefox
Classifications
CWE-787, T1203
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 27, 2023CVE publishedPublication date reported by the CVE source.
  2. May 1, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=unspecified <118

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Mozilla · Firefoxversion=unspecified <118
Mozilla · Thunderbirdversion=unspecified <115.3
Mozilla · Firefox ESRversion=unspecified <115.3

Published CVSS scores

9.8CISA-ADPCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
9.8NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-787Out-of-bounds Write
T1203Exploitation for Client Execution

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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