CVE-2026-8958: mozilla firefox Exposure of Resource to Wrong Sphere
CVSS: 8.6v3.1HighAnalyzed
AliasesUBUNTU-CVE-2026-8958DEBIAN-CVE-2026-8958CGA-6j39-r65j-6f98CGA-f45w-8984-cpf6CGA-9r2g-wmx7-3xvgCGA-r95f-m58w-xqcg
Published 19-05-2026Last modified 19-05-2026
Vulnerability summary
CVE-2026-8958 is a high (CVSS 8.6) Exposure of Resource to Wrong Sphere vulnerability in mozilla firefox. EPSS estimates a 0.44% chance of exploitation in the next 30 days, higher than 36.7% of scored vulnerabilities.
CVSS score
8.6/10
010
High · v3.1 (CVE.org)EPSS score
0.44%
0%100%
Low · +0.09 pp in 30 daysKEVNot listedIn no KEV catalog
RansomwareNone recordedNo known use recorded
Public exploits0No public exploits recorded
Advisory lineage
Upstream 0 · Downstream 27 · Related 5MGASA-2026-0164MGASA-2026-0165OPENSUSE-SU-2026:10813-1OPENSUSE-SU-2026:10863-1OPENSUSE-SU-2026:10864-1OPENSUSE-SU-2026:21168-1RHSA-2026:21378RHSA-2026:21380RHSA-2026:21381RHSA-2026:21382RHSA-2026:22325RHSA-2026:22643RHSA-2026:26174RHSA-2026:26268RHSA-2026:26269RHSA-2026:26270RHSA-2026:26491RHSA-2026:26492RHSA-2026:26493RHSA-2026:26521RHSA-2026:26536RHSA-2026:26539RHSA-2026:26551RHSA-2026:26606RHSA-2026:26629RHSA-2026:26630RHSA-2026:27715CGA-PF23-R9J2-P5P9
Timeline
- 19-05-2026PublishedVulnerability first disclosed.
- 19-05-2026Last modifiedVulnerability information updated.
Description
Information disclosure, sandbox escape in the Security: Process Sandboxing component. This vulnerability was fixed in Firefox 151, Firefox ESR 140.11, Thunderbird 151, and Thunderbird 140.11.
CVSS metrics
4 scores · 4 sources · 1 versionHigh 8.6Preferred score · CVE.org (CNA)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:N/A:NSourcesAll 4 agree
- OSV · UbuntuEcosystem advisory · calculated8.6HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:N/A:N
- OSV · DebianEcosystem advisory · calculated8.6HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:N/A:N
- NVDNIST8.6HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:N/A:N
EPSS trend
Probability
0.44%
Chance of exploitation in the next 30 days
Percentile
37%
Versus all other CVEs
30-day change
+0.09 pp
From 0.34% on 19-09-2026
19-09-202619-10-2026
EPSS score0.44%
Known exploited
Compare KEV catalogsNot in any of the 3 tracked catalogs.
Public exploits
0 foundNo public exploits indexed.
Weaknesses
CWE · root cause- CWE-668Exposure of Resource to Wrong SphereThe product exposes a resource to the wrong control sphere, providing unintended actors with inappropriate access to the resource.
- CWE-693Protection Mechanism FailureThe product does not use or incorrectly uses a protection mechanism that provides sufficient defense against directed attacks against the product.
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)
Chainguard2 products
- firefox< 140.11-r0
- firefox-esr< 140.11-r0
Debian2 products
- firefox-esr< 140.11.0esr-1~deb12u1 | < 140.11.0esr-1~deb13u1 | < 140.11.0esr-1
- thunderbird< 1:140.11.0esr-1~deb12u1 | < 1:140.11.0esr-1~deb13u1 | < 1:140.11.0esr-1
Mozilla2 products
- firefox< 140.11.0 | < 151.0.0
- thunderbird< 140.11 | < 151.0.0
Wolfi1 product
- firefox< 140.11-r0
5 vendors · 15 products
