CVE-2025-8037Public exploitNetwork attack vector

Secure-cookie shadowing via nameless equals-sign values

Published Jul 22, 2025 · Updated Jul 29, 2026

Cookie validation in Firefox and Thunderbird allows remote attackers to shadow Secure cookies from an insecure same-site origin. CookieValidation::CheckValue accepted an empty cookie name whose value contained an equals sign, bypassing the name comparison that protects existing Secure cookies. The victim must reach an attacker-controlled HTTP origin within the target site's registrable domain; affected releases are before 141 and ESR before 140.1, and downstream impact depends on the shadowed cookie's use.

CVSS severity9.1
Critical
EPSS probability0.22%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

Cookie validation in Firefox and Thunderbird allows remote attackers to shadow Secure cookies from an insecure same-site origin. CookieValidation::CheckValue accepted an empty cookie name whose value contained an equals sign, bypassing the name comparison that protects existing Secure cookies. The victim must reach an attacker-controlled HTTP origin within the target site's registrable domain; affected releases are before 141 and ESR before 140.1, and downstream impact depends on the shadowed cookie's use.

The record

CVE
CVE-2025-8037
Published
Jul 22, 2025
Updated
Jul 29, 2026
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-614
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jul 22, 2025CVE publishedPublication date reported by the CVE source.
  2. Jul 29, 2026Record 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?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

9.1CISA-ADPCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/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.

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

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-614Sensitive Cookie in HTTPS Session Without 'Secure' Attribute

Public exploit references

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

Technologies

Your stack

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo