CVE-2026-6779: mozilla firefox Improper Input Validation
CVSS: 5.3v3.1MediumAnalyzed
AliasesUBUNTU-CVE-2026-6779CGA-2gv3-pq3p-cr83CGA-x9h7-9gc7-7rrv
Published 21-04-2026Last modified 26-05-2026
Vulnerability summary
CVE-2026-6779 is a medium (CVSS 5.3) Improper Input Validation vulnerability in mozilla firefox. EPSS estimates a 0.34% chance of exploitation in the next 30 days, higher than 26.6% of scored vulnerabilities.
CVSS score
5.3/10
010
Medium · v3.1 (CVE.org)EPSS score
0.34%
0%100%
Low · +0.14 pp in 30 daysKEVNot listedIn no KEV catalog
RansomwareNone recordedNo known use recorded
Public exploits0No public exploits recorded
Advisory lineage
Upstream 0 · Downstream 2 · Related 3Timeline
- 21-04-2026PublishedVulnerability first disclosed.
- 26-05-2026Last modifiedVulnerability information updated.
Description
Other issue in the JavaScript Engine component. This vulnerability was fixed in Firefox 150 and Thunderbird 150.
CVSS metrics
3 scores · 3 sources · 1 versionMedium 5.3Preferred score · CVE.org (CNA)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:NSourcesAll 3 agree
- OSV · UbuntuEcosystem advisory · calculated5.3MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
- NVDNIST5.3MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
EPSS trend
Probability
0.34%
Chance of exploitation in the next 30 days
Percentile
27%
Versus all other CVEs
30-day change
+0.14 pp
From 0.21% on 22-09-2026
22-09-202622-10-2026
EPSS score0.34%
Known exploited
Compare KEV catalogsNot in any of the 3 tracked catalogs.
Public exploits
0 foundNo public exploits indexed.
Weaknesses
CWE · root cause- CWE-20Improper Input ValidationThe product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly.
- CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users.
- CWE-119Improper Restriction of Operations within the Bounds of a Memory BufferThe product performs operations on a memory buffer, but it reads from or writes to a memory location outside the buffer's intended boundary. This may result in read or write operations on unexpected memory locations that could be linked to other variables, data structures, or internal program data.
Affected systems
Ubuntu8 products
- mozjs102All versions (No fix recorded)
- mozjs115All versions (No fix recorded)
- mozjs38All versions (No fix recorded)
- mozjs52All versions (No fix recorded)
- mozjs68All versions (No fix recorded)
Mozilla2 products
- firefox< 150.0
- thunderbird< 150.0
Chainguard1 product
- firefox< 150-r0
Wolfi1 product
- firefox< 150-r0
4 vendors · 12 products
References
6 links- bugzilla.mozilla.org/show_bug.cgi?id=2023343Permissions Required
- www.mozilla.org/security/advisories/mfsa2026-30/Vendor Advisory
- www.mozilla.org/security/advisories/mfsa2026-33/Vendor Advisory