CVE-2023-4578Public exploitNetwork attack vector

Client crash via out-of-memory exception mishandling

Published Sep 11, 2023 · Updated Dec 18, 2025

Resource exhaustion in Firefox before 117, Firefox ESR before 115.2, and Thunderbird before 115.2 allows remote attackers to crash clients. JS::CheckRegExpSyntax can set a syntax error, after which convertToRuntimeErrorAndClear allocates during exhausted memory and misclassifies the new out-of-memory exception as that syntax error. Exploitation requires user interaction with crafted web content that first exhausts process memory; ordinary Thunderbird email reading disables scripting.

CVSS severity6.5
Medium
EPSS probability0.62%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Resource exhaustion in Firefox before 117, Firefox ESR before 115.2, and Thunderbird before 115.2 allows remote attackers to crash clients. JS::CheckRegExpSyntax can set a syntax error, after which convertToRuntimeErrorAndClear allocates during exhausted memory and misclassifies the new out-of-memory exception as that syntax error. Exploitation requires user interaction with crafted web content that first exhausts process memory; ordinary Thunderbird email reading disables scripting.

The record

CVE
CVE-2023-4578
Published
Sep 11, 2023
Updated
Dec 18, 2025
Vendor
Mozilla
Product
Firefox
Classifications
CWE-770, T1499
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 11, 2023CVE publishedPublication date reported by the CVE source.
  2. Dec 18, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

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

  1. Affected versionversion=unspecified <117

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Mozilla · Firefoxversion=unspecified <117
Mozilla · Thunderbirdversion=unspecified <115.2
Mozilla · Firefox ESRversion=unspecified <115.2

Published CVSS scores

6.5NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/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.

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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 exploitPublished

Weakness, pattern, technique

CWE-770Allocation of Resources Without Limits or Throttling
T1499Endpoint Denial of Service

Public exploit references

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Technologies

Your stack

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Your stack

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