CVE-2023-5723Public exploitNetwork attack vector

Site disruption via malformed cookie names

Published Oct 24, 2023 · Updated Feb 13, 2025

Cookie validation in Mozilla Firefox before 119 allows context-dependent attackers to disrupt sites through malformed cookie names. CookieCommons::CheckName omits DEL, semicolon, and equals from its illegal-name set, so document.cookie accepts names forbidden by cookie syntax. Exploitation requires temporary script access to the target site, and the demonstrated consequence is site breakage from invalid cookie state.

CVSS severity5.3
Medium
EPSS probability0.69%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Cookie validation in Mozilla Firefox before 119 allows context-dependent attackers to disrupt sites through malformed cookie names. CookieCommons::CheckName omits DEL, semicolon, and equals from its illegal-name set, so document.cookie accepts names forbidden by cookie syntax. Exploitation requires temporary script access to the target site, and the demonstrated consequence is site breakage from invalid cookie state.

The record

CVE
CVE-2023-5723
Published
Oct 24, 2023
Updated
Feb 13, 2025
Vendor
Mozilla
Product
Firefox
Classifications
Unavailable
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Oct 24, 2023CVE publishedPublication date reported by the CVE source.
  2. Feb 13, 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 <119

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Mozilla · Firefoxversion=unspecified <119

Published CVSS scores

5.3NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N

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

No sourced classifications are available.

Public exploit references

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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