How severe is CVE-2019-11743?

CVE-2019-11743 has a CVSS 3.x base score of 3.7, rated low severity. It is exploitable over network with high attack complexity, requires no privileges and no user interaction. Impact on confidentiality is low, integrity none, and availability none.

Is CVE-2019-11743 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (76th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2019-11743?

CVE-2019-11743 primarily affects Mozilla Firefox. In total, 3 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2019-11743?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

When was CVE-2019-11743 published?

CVE-2019-11743 was published on 2019-09-27 and last updated on 2026-06-17.

CVE-2019-11743

CVE-2019-11743 is a low-severity vulnerability in Mozilla Firefox with a CVSS 3.x base score of 3.7. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-203.

Key facts

Severity: Low (CVSS 3.x base score 3.7)
CVSS v2: 4.3
EPSS exploit prediction: 2% (76th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-203
Affected product: Mozilla Firefox
Published: 2019-09-27
Last modified: 2026-06-17

Description

Navigation events were not fully adhering to the W3C's "Navigation-Timing Level 2" draft specification in some instances for the unload event, which restricts access to detailed timing attributes to only be same-origin. This resulted in potential cross-origin information exposure of history through timing side-channel attacks. This vulnerability affects Firefox < 69, Thunderbird < 68.1, Thunderbird < 60.9, Firefox ESR < 60.9, and Firefox ESR < 68.1.

Frequently asked questions

What is CVE-2019-11743?: Navigation events were not fully adhering to the W3C's "Navigation-Timing Level 2" draft specification in some instances for the unload event, which restricts access to detailed timing attributes to only be same-origin. This resulted in potential cross-origin information exposure of history through timing side-channel attacks. This vulnerability affects Firefox < 69, Thunderbird < 68.1, Thunderbird < 60.9, Firefox ESR < 60.9, and Firefox ESR < 68.1.
How severe is CVE-2019-11743?: CVE-2019-11743 has a CVSS 3.x base score of 3.7, rated low severity. It is exploitable over network with high attack complexity, requires no privileges and no user interaction. Impact on confidentiality is low, integrity none, and availability none.
Is CVE-2019-11743 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (76th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2019-11743?: CVE-2019-11743 primarily affects Mozilla Firefox. In total, 3 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2019-11743?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2019-11743 published?: CVE-2019-11743 was published on 2019-09-27 and last updated on 2026-06-17.

References

Affected products (3)

cpe:2.3:a:mozilla:firefox:*:*:*:*:*:*:*:*
cpe:2.3:a:mozilla:firefox_esr:*:*:*:*:*:*:*:*
cpe:2.3:a:mozilla:thunderbird:*:*:*:*:*:*:*:*

More vulnerabilities in Mozilla Firefox

CVE-2026-4725 — Critical (CVSS 10.0): Sandbox escape due to use-after-free in the Graphics: Canvas2D component. This vulnerability was fixed in Firefox 149…
CVE-2026-4692 — Critical (CVSS 10.0): Sandbox escape in the Responsive Design Mode component. This vulnerability was fixed in Firefox 149, Firefox ESR…
CVE-2026-4689 — Critical (CVSS 10.0): Sandbox escape due to incorrect boundary conditions, integer overflow in the XPCOM component. This vulnerability was…
CVE-2026-4688 — Critical (CVSS 10.0): Sandbox escape due to use-after-free in the Disability Access APIs component. This vulnerability was fixed in Firefox…
CVE-2026-2778 — Critical (CVSS 10.0): Sandbox escape due to incorrect boundary conditions in the DOM: Core & HTML component. This vulnerability was fixed in…
CVE-2026-2776 — Critical (CVSS 10.0): Sandbox escape due to incorrect boundary conditions in the Telemetry component in External Software. This vulnerability…

All CVEs affecting Mozilla Firefox →

Other CWE-203 (Observable Discrepancy) vulnerabilities

CVE-2019-25337 — Critical (CVSS 9.8): OwnCloud 8.1.8 contains a username enumeration vulnerability that allows remote attackers to discover user accounts by…
CVE-2026-23519 — Critical (CVSS 9.8): RustCrypto CMOV provides conditional move CPU intrinsics which are guaranteed on major platforms to execute in…
CVE-2025-27667 — Critical (CVSS 9.8): Vasion Print (formerly PrinterLogic) before Virtual Appliance Host 22.0.843 Application 20.0.1923 allows Administrative…
CVE-2024-25714 — Critical (CVSS 9.8): In Rhonabwy through 1.1.13, HMAC signature verification uses a strcmp function that is vulnerable to side-channel…
CVE-2024-25191 — Critical (CVSS 9.8): php-jwt 1.0.0 uses strcmp (which is not constant time) to verify authentication, which makes it easier to bypass…
CVE-2024-25190 — Critical (CVSS 9.8): l8w8jwt 2.2.1 uses memcmp (which is not constant time) to verify authentication, which makes it easier to bypass…

Browse all CWE-203 (Observable Discrepancy) vulnerabilities →