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No exploitation reportedFix available

CVE-2026-100771

Undefined behavior in the DOM: Streams component

No exploitation reported by the sources we read.

  • Published2026-09-29
  • Fixed in157.0.0 · 153.4.0 · 140.17.0 · 115.42.0
  • WeaknessCWE-758

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

Undefined behavior in the DOM: Streams component. This vulnerability was fixed in Firefox ESR 153.4, Thunderbird 157, Thunderbird 140.17, Thunderbird 153.4, Firefox 157, Firefox ESR 115.42, and Firefox ESR 140.17.

Timeline

dates in UTC
  1. 2026-09-2913:17CVE publishedNVD

Observed activity

isMalicious corpus · updated 2026-10-23 18:48 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-2026-100771?format=txt
  • CSV export: https://api.ismalicious.com/edl/cve/CVE-2026-100771?format=csv
  • TAXII collection of exploited CVEs
  • The EDL and CSV take an API key on the Pro plan.

Versions per branch

NVD
Mozilla firefox
BranchAffectedFixed in
157.0≥ 154.0.0, < 157.0.0157.0.0
153.x≥ 153.0, < 153.4.0153.4.0
140.x≥ 140.0.0, < 140.17.0140.17.0
115.x≥ 115.0, < 115.42.0115.42.0
Mozilla thunderbird
BranchAffectedFixed in
157.0≥ 154.0, < 157.0157.0
153.x≥ 153.0, < 153.4.0153.4.0
140.x≥ 140.0, < 140.17.0140.17.0

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.

Vendor advisories

  • CVE-2026-100771 Red Hat Product Security23 known affected

    firefox: thunderbird: Undefined behavior in the DOM: Streams component

    firefox as a component of Red Hat Enterprise Linux 10 · firefox.src as a component of Red Hat Enterprise Linux 10 · rhel10/firefox-flatpak as a component of Red Hat Enterprise Linux 10 · +20 more

Full record on NVD

Fix

  1. Update Mozilla firefox to 157.0.0 · 153.4.0 · 140.17.0 · 115.42.0
  2. Workaround from the vendor Red Hat Product Security CVE-2026-100771 · 23 productsMitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability.
  3. No fix available, says the vendor Red Hat Product Security CVE-2026-100771 · 17 productsAffected
  4. No fix planned, says the vendor Red Hat Product Security CVE-2026-100771 · 6 productsOut of support scope

Advisories and patches

Detection

Nuclei template
none so far
ProjectDiscovery
Exploit-DB
no entry
Exploit-DB
Proof-of-concept repositories
none listed
PoC-in-GitHub

Sources

Technical details

CVSS v3 Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N
Published
2026-09-29
Last Modified
2026-10-06
NVD status
Analyzed

Frequently asked questions

What is CVE-2026-100771?

Undefined behavior in the DOM: Streams component. This vulnerability was fixed in Firefox ESR 153.4, Thunderbird 157, Thunderbird 140.17, Thunderbird 153.4, Firefox 157, Firefox ESR 115.42, and Firefox ESR 140.17.

Is CVE-2026-100771 actively exploited?

Active exploitation of CVE-2026-100771 has not been confirmed. Its EPSS score was 0.3% on 2026-10-22, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2026-100771?

CVE-2026-100771 has a CVSS v3 base score of 8.1 (HIGH severity), with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N.

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