CVE-2024-0743Network attack vector

Client crash via unchecked TLS send length

Published Jan 23, 2024 · Updated Nov 3, 2025

NSS TLS code in Firefox before 122, Firefox ESR before 115.9, and Thunderbird before 115.9 allows remote attackers to crash the client. ssl_SendSavedWriteData accepts an ssl_DefSend return larger than pendingBuf.len, subtracts it from the unsigned length, and passes an invalid offset and size to memmove. No authentication or user interaction is required; a remote TLS peer can trigger the out-of-bounds access, with the established impact limited to a client crash.

CVSS severity7.5
High
EPSS probability1.29%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

NSS TLS code in Firefox before 122, Firefox ESR before 115.9, and Thunderbird before 115.9 allows remote attackers to crash the client. ssl_SendSavedWriteData accepts an ssl_DefSend return larger than pendingBuf.len, subtracts it from the unsigned length, and passes an invalid offset and size to memmove. No authentication or user interaction is required; a remote TLS peer can trigger the out-of-bounds access, with the established impact limited to a client crash.

The record

CVE
CVE-2024-0743
Published
Jan 23, 2024
Updated
Nov 3, 2025
Vendor
Mozilla
Product
Firefox
Classifications
CWE-252, T1203
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jan 23, 2024CVE publishedPublication date reported by the CVE source.
  2. Nov 3, 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 <122

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Mozilla · Firefoxversion=unspecified <122
Mozilla · Thunderbirdversion=unspecified <115.9
Mozilla · Firefox ESRversion=unspecified <115.9

Published CVSS scores

7.5CISA-ADPCVSS:3.1/AV:N/AC:L/PR:N/UI:N/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.

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 exploitUnconfirmed

Weakness, pattern, technique

CWE-252Unchecked Return Value
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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