CVE-2026-100783: firefox — Fix

Description

Uninitialized memory in the Audio/Video 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.

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CVSS v3.1 Score

4.3

MEDIUM

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:L

EPSS — Exploit Prediction

0.0028

Probability of exploitation

0.19%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-457 CWE-457

Affected Products

Vendor	Product	Versions
mozilla	firefox	< 115.42.0
mozilla	firefox	116.0 — 140.17.0
mozilla	firefox	141.0 — 153.4.0
mozilla	firefox	154.0.0 — 157.0.0
mozilla	thunderbird	< 140.17.0
mozilla	thunderbird	141.0 — 153.4.0
mozilla	thunderbird	154.0 — 157.0

References

Advisories & Patches

https://www.mozilla.org/security/advisories/mfsa2026-100/ https://www.mozilla.org/security/advisories/mfsa2026-101/ https://www.mozilla.org/security/advisories/mfsa2026-102/ https://www.mozilla.org/security/advisories/mfsa2026-103/ https://www.mozilla.org/security/advisories/mfsa2026-97/ https://www.mozilla.org/security/advisories/mfsa2026-98/ https://www.mozilla.org/security/advisories/mfsa2026-99/

Other References

https://bugzilla.mozilla.org/show_bug.cgi?id=2069804

Frequently Asked Questions

What is CVE-2026-100783? +

Uninitialized memory in the Audio/Video 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. It has a CVSS v3.1 base score of 4.3 (MEDIUM).

How severe is CVE-2026-100783? +

CVE-2026-100783 has a CVSS v3.1 score of 4.3 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance. The EPSS score is 0.0028, placing it in the 0th percentile for exploitation probability.

What products are affected by CVE-2026-100783? +

CVE-2026-100783 affects products from mozilla, specifically: firefox, thunderbird. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2026-100783? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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