CVE-2025-1936Public exploitNetwork attack vector

JavaScript execution via null-byte JAR entry mismatch

Published Mar 4, 2025 · Updated Apr 13, 2026

Null-byte handling in Firefox and Thunderbird allows attackers to execute disguised JavaScript through a crafted jar: URL. nsJARChannel::LookupFile percent-decodes the archive entry, but nsZipArchive::GetItem used strlen on a character pointer and truncated lookup at an embedded NUL while MIME detection retained the later suffix. Exploitation requires a crafted WebExtension or other JAR resource; the lookup mismatch lets code hidden in image metadata run as JavaScript.

CVSS severity7.3
High
EPSS probability0.44%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Null-byte handling in Firefox and Thunderbird allows attackers to execute disguised JavaScript through a crafted jar: URL. nsJARChannel::LookupFile percent-decodes the archive entry, but nsZipArchive::GetItem used strlen on a character pointer and truncated lookup at an embedded NUL while MIME detection retained the later suffix. Exploitation requires a crafted WebExtension or other JAR resource; the lookup mismatch lets code hidden in image metadata run as JavaScript.

The record

CVE
CVE-2025-1936
Published
Mar 4, 2025
Updated
Apr 13, 2026
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-158, T1036, T1059.007
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Mar 4, 2025CVE publishedPublication date reported by the CVE source.
  2. Apr 13, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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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

7.3CISA-ADPCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L

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 exploitPublished

Weakness, pattern, technique

CWE-158Improper Neutralization of Null Byte or NUL Character
T1036Masquerading
T1059.007JavaScript/JScript

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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