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Public proof of conceptFix available

CVE-2019-9791

A public proof of concept exists; no exploitation attested.

  • Published2019-04-26
  • WeaknessCWE-843

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

Description

The type inference system allows the compilation of functions that can cause type confusions between arbitrary objects when compiled through the IonMonkey just-in-time (JIT) compiler and when the constructor function is entered through on-stack replacement (OSR). This allows for possible arbitrary reading and writing of objects during an exploitable crash. This vulnerability affects Thunderbird < 60.6, Firefox ESR < 60.6, and Firefox < 66.

Timeline

dates in UTC
  1. 2019-03-26Exploit-DB entryExploit-DB
  2. 2019-04-2617:29CVE publishedNVD

Observed activity

isMalicious corpus · updated 2026-11-03 21:37 UTC
Indicators tagged with this CVE, per day0 indicators over 7 days
Block these indicators
  • Firewall list (EDL, text): https://api.ismalicious.com/edl/cve/CVE-2019-9791?format=txt
  • CSV export: https://api.ismalicious.com/edl/cve/CVE-2019-9791?format=csv
  • TAXII collection of exploited CVEs
  • The EDL and CSV take an API key on the Pro plan.

Versions per branch

NVD
Redhat enterprise linux eus
BranchAffectedFixed in
8.1= 8.1no fix published
8.2= 8.2no fix published
8.4= 8.4no fix published
Mozilla firefox
BranchAffectedFixed in
66.0< 66.066.0
60.6< 60.6.060.6.0
Redhat enterprise linux server aus
BranchAffectedFixed in
8.2= 8.2no fix published
8.4= 8.4no fix published

3 more products in the sources.

as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.

Distribution builds and vendor advisories

Packages from OSV.dev and products from the vendors' CSAF advisories.

version not verifiedVersions not verified: read as OSV.dev and the vendors publish them, not checked against each vendor's release list.

Packages

  • firefoxUbuntu:18.04:LTSall versions · fixed in 66.0+build3-0ubuntu0.18.04.1
  • firefoxUbuntu:16.04:LTSall versions · fixed in 66.0+build3-0ubuntu0.16.04.2
  • firefoxUbuntu:14.04:LTSall versions · fixed in 66.0.1+build1-0ubuntu0.14.04.1
  • firefoxRed Hat:enterprise_linux:8::appstreamall versions · fixed in 0:60.6.1-1.el8and 5 other packages
  • firefoxRed Hat:enterprise_linux:7::workstationall versions · fixed in 0:60.6.0-3.el7_6and 1 other package
  • firefoxRed Hat:enterprise_linux:7::serverall versions · fixed in 0:60.6.0-3.el7_6and 1 other package
  • firefoxRed Hat:enterprise_linux:7::clientall versions · fixed in 0:60.6.0-3.el7_6and 1 other package
  • firefoxRed Hat:enterprise_linux:6::workstationall versions · fixed in 0:60.6.0-3.el6_10and 1 other package

69 more package ranges on OSV.dev

Vendor advisories

  • CVE-2019-9791 Red Hat Product Security229 products fixed

    Mozilla: Type inference is incorrect for constructors entered through on-stack replacement with IonMonkey

  • RHSA-2019:1144 Red Hat Product Security7 products fixed

    Red Hat Security Advisory: thunderbird security update

  • RHSA-2019:0966 Red Hat Product Security13 products fixed

    Red Hat Security Advisory: firefox security update

  • RHSA-2019:0681 Red Hat Product Security16 products fixed

    Red Hat Security Advisory: thunderbird security update

  • RHSA-2019:0680 Red Hat Product Security19 products fixed

    Red Hat Security Advisory: thunderbird security update

  • RHSA-2019:0623 Red Hat Product Security30 products fixed

    Red Hat Security Advisory: firefox security update

1 more advisory

Full record on NVD

Fix

  1. Vendor fix Red Hat Product Security RHSA-2019:1144 · 7 productsFor details on how to apply this update, which includes the changes described in this advisory, refer to: https://access.redhat.com/articles/11258 All running instances of Thunderbird must be restarted for the update to take effect.
  2. Vendor fix Red Hat Product Security RHSA-2019:0966 · 13 productsFor details on how to apply this update, which includes the changes described in this advisory, refer to: https://access.redhat.com/articles/11258 After installing the update, Firefox must be restarted for the changes to take effect.

Advisories and patches

Detection

read 2026-11-02 22:42 UTC
Nuclei template
none so far
ProjectDiscovery
Exploit-DB
EDB-46613
Exploit-DB
Proof-of-concept repositories
1 repository, unverifiedSp0pielar/CVE-2019-9791
PoC-in-GitHub
Metasploit modules
none listed
Metasploit Framework

Sources

  • NVDCVSS 3.19.8read 2026-10-23
  • NVDCVSS 2.07.5read 2026-10-23
  • NVDweakness (CWE)CWE-843read 2026-10-23
  • FIRST EPSSEPSS score19.9 %read 2026-11-02
  • PoC-in-GitHubproof of concept1read 2026-11-02
  • Exploit-DBdetectionread 2026-11-02
  • OSVaffected packages—

Identifiers

Technical details

CVSS v3 Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Published
2019-04-26
Last Modified
2026-06-17
NVD status
Modified

Frequently asked questions

What is CVE-2019-9791?

The type inference system allows the compilation of functions that can cause type confusions between arbitrary objects when compiled through the IonMonkey just-in-time (JIT) compiler and when the constructor function is entered through on-stack replacement (OSR). This allows for possible arbitrary reading and writing of objects during an exploitable crash. This vulnerability affects Thunderbird < 60.6, Firefox ESR < 60.6, and Firefox < 66.

Is CVE-2019-9791 actively exploited?

Active exploitation of CVE-2019-9791 has not been confirmed. Its EPSS score was 19.9% on 2026-11-03, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2019-9791?

CVE-2019-9791 has a CVSS v3 base score of 9.8 (CRITICAL severity), with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.

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