CVE-2026-100783
MEDIUM 4.3Uninitialized 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.
NO EXPLOITATION SIGNALS
No known exploitation, public exploit, or elevated probability at this time. Track for changes.
Exploitation likelihood
0.3%chance of exploitation in 30 days · 19th percentile
○ In CISA KEV
○ Public exploit / PoC
Impact if exploited
4.3CVSS 3.1 · MEDIUM
- ConfidentialityNone
- IntegrityNone
- AvailabilityLow
What an attacker needs
- ✓Access: Reachable over the network — no local access needed
- ✓Privileges: No account or privileges required
- ⚠User interaction: A user must take an action (click / open a file)
- ✓Complexity: No special conditions — reliably repeatable
✓ lowers the bar for an attacker · ⚠ raises it
Proof of concept & exploit code
- github-search Search GitHub for public PoC repos
Test against your own equipment
curl -s https://vulnpedia.com/cve/CVE-2026-100783/poc.jsonMachine-readable PoC index for this CVE (for automation).Listed for defensive triage, patch verification, and authorized testing on systems you own. Machine-readable: /cve/CVE-2026-100783/poc.json
Weakness (CWE)
- CWE-457: Use of Uninitialized Variable
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:L
Known Affected Software Configurations
| Vendor | Product | Version range |
|---|---|---|
| Mozilla | Firefox | < 115.42.0 |
| Mozilla | Firefox | ≥ 116.0 and < 140.17.0 |
| Mozilla | Firefox | ≥ 141.0 and < 153.4.0 |
| Mozilla | Firefox | ≥ 154.0.0 and < 157.0.0 |
| Mozilla | Thunderbird | < 140.17.0 |
| Mozilla | Thunderbird | ≥ 141.0 and < 153.4.0 |
| Mozilla | Thunderbird | ≥ 154.0 and < 157.0 |
All CVSS metrics
- MEDIUM 4.3 v3.1 · ADP Primary
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:L - MEDIUM 4.3 v3.1 · NVD Secondary
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:L
References
Advisories
- 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/