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CVE-2021-43542Using XMLHttpRequest, an attacker could have identified installed applications by probing error messages for loading external protocols.…
- 6.5MediumCVSS base score
- 1.8%Exploitation in 30 daysEPSS · top 21% of all CVEs
- NoKnown exploitednot in CISA's KEV catalog
- NonePublic exploitsnone known yet
Description
Using XMLHttpRequest, an attacker could have identified installed applications by probing error messages for loading external protocols. This vulnerability affects Thunderbird < 91.4.0, Firefox ESR < 91.4.0, and Firefox < 95.
Timeline
ID reserved
By mozilla
- 30 days later
· 30 days later
Published
- 3 years later
· 3 years later
Record updated
Changes after publication (a new score, a public exploit, EPSS crossing 1, 10 or 50 %, leaving KEV) are kept since November 2026; earlier ones are not known.
Scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| NVDNVD · Modified | 3.1 | Medium6.5 | CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N |
- EPSS (exploitation in 30 days)
- 1.8% · top 21% of all CVEs (12 Nov 2026)
Loading the EPSS history…
The list uses the assigner's score when there is one, then CISA's, then NVD's: Medium 6.5.
Affected products
- affected unspecified – < 91.4.0
- affected unspecified – < 91.4.0
- affected unspecified – < 95
References
References10
- https://www.mozilla.org/security/advisories/mfsa2021-53/ (opens in a new tab)x_refsource_MISCx_transferred
- https://www.mozilla.org/security/advisories/mfsa2021-54/ (opens in a new tab)x_refsource_MISCx_transferred
- https://www.mozilla.org/security/advisories/mfsa2021-52/ (opens in a new tab)x_refsource_MISCx_transferred
- https://bugzilla.mozilla.org/show_bug.cgi?id=1723281 (opens in a new tab)x_refsource_MISCx_transferred
- DSA-5026 (opens in a new tab)vendor-advisoryx_refsource_DEBIANx_transferred
- [debian-lts-announce] 20211229 [SECURITY] [DLA 2863-1] firefox-esr security update (opens in a new tab)mailing-listx_refsource_MLISTx_transferred
- DSA-5034 (opens in a new tab)vendor-advisoryx_refsource_DEBIANx_transferred
- [debian-lts-announce] 20220104 [SECURITY] [DLA 2874-1] thunderbird security update (opens in a new tab)mailing-listx_refsource_MLISTx_transferred
- GLSA-202202-03 (opens in a new tab)vendor-advisoryx_refsource_GENTOOx_transferred
- GLSA-202208-14 (opens in a new tab)vendor-advisoryx_refsource_GENTOOx_transferred
Sources
The same CVE in the primary databases and aggregators, to check against.
- CVE.org record (opens in a new tab)
- CVE List JSON (GitHub) (opens in a new tab)
- NVD (opens in a new tab)
- FIRST EPSS (opens in a new tab)
- EUVD EUVD-2021-30471 (opens in a new tab)
- OSV.dev (opens in a new tab)
- GitHub Advisories (opens in a new tab)
- CIRCL Vulnerability-Lookup (opens in a new tab)
Badge for a README or a ticket
[](https://cveledger.app/cve/CVE-2021-43542)Record last updated .