CVE-2019-11745Network attack vector

Client crash via undersized NSS encryption buffer

Published Jan 8, 2020 · Updated Aug 4, 2024

Out-of-bounds write in Firefox before 71, Firefox ESR and Thunderbird before 68.3 allows attackers to crash clients via undersized output. NSC_EncryptUpdate passes the block size instead of the caller's smaller maximum output length to a padded encryption update, then advances the output pointer and underflows the unsigned remaining-length counter. Reaching the overwrite requires multipart block-cipher use with padding and an undersized output buffer; Mozilla identified SRTP as the Firefox path and excluded WebCrypto.

CVSS severity8.8
High
EPSS probability2.99%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Out-of-bounds write in Firefox before 71, Firefox ESR and Thunderbird before 68.3 allows attackers to crash clients via undersized output. NSC_EncryptUpdate passes the block size instead of the caller's smaller maximum output length to a padded encryption update, then advances the output pointer and underflows the unsigned remaining-length counter. Reaching the overwrite requires multipart block-cipher use with padding and an undersized output buffer; Mozilla identified SRTP as the Firefox path and excluded WebCrypto.

The record

CVE
CVE-2019-11745
Published
Jan 8, 2020
Updated
Aug 4, 2024
Vendor
Mozilla
Product
Firefox
Classifications
CWE-787, T1203
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jan 8, 2020CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 2024Record 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=before 71

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Mozilla · Firefoxversion=before 71
Mozilla · Thunderbirdversion=before 68.3
Mozilla · Firefox ESRversion=before 68.3

Published CVSS scores

6.8NIST NVDAV:N/AC:M/Au:N/C:P/I:P/A:P
8.8NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/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-787Out-of-bounds Write
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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