Vulnerability Details : CVE-2021-38507
The Opportunistic Encryption feature of HTTP2 (RFC 8164) allows a connection to be transparently upgraded to TLS while retaining the visual properties of an HTTP connection, including being same-origin with unencrypted connections on port 80. However, if a second encrypted port on the same IP address (e.g. port 8443) did not opt-in to opportunistic encryption; a network attacker could forward a connection from the browser to port 443 to port 8443, causing the browser to treat the content of port 8443 as same-origin with HTTP. This was resolved by disabling the Opportunistic Encryption feature, which had low usage. This vulnerability affects Firefox < 94, Thunderbird < 91.3, and Firefox ESR < 91.3.
Exploit prediction scoring system (EPSS) score for CVE-2021-38507
Probability of exploitation activity in the next 30 days: 0.22%
Percentile, the proportion of vulnerabilities that are scored at or less: ~ 59 % EPSS Score History EPSS FAQ
CVSS scores for CVE-2021-38507
| Base Score | Base Severity | CVSS Vector | Exploitability Score | Impact Score | Score Source |
|---|---|---|---|---|---|
|
4.3
|
MEDIUM | AV:N/AC:M/Au:N/C:N/I:P/A:N |
8.6
|
2.9
|
NIST |
|
6.5
|
MEDIUM | CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N |
2.8
|
3.6
|
NIST |
CWE ids for CVE-2021-38507
-
The product does not properly verify that the source of data or communication is valid.Assigned by: nvd@nist.gov (Primary)
References for CVE-2021-38507
-
https://lists.debian.org/debian-lts-announce/2022/01/msg00001.html
[SECURITY] [DLA 2874-1] thunderbird security updateMailing List;Third Party Advisory
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https://bugzilla.mozilla.org/show_bug.cgi?id=1730935
Access DeniedIssue Tracking;Permissions Required;Vendor Advisory
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https://lists.debian.org/debian-lts-announce/2021/12/msg00030.html
[SECURITY] [DLA 2863-1] firefox-esr security updateMailing List;Third Party Advisory
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https://www.debian.org/security/2021/dsa-5026
Debian -- Security Information -- DSA-5026-1 firefox-esrThird Party Advisory
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https://www.mozilla.org/security/advisories/mfsa2021-50/
Security Vulnerabilities fixed in Thunderbird 91.3 — MozillaVendor Advisory
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https://security.gentoo.org/glsa/202202-03
Mozilla Firefox: Multiple vulnerabilities (GLSA 202202-03) — Gentoo securityThird Party Advisory
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https://www.mozilla.org/security/advisories/mfsa2021-49/
Security Vulnerabilities fixed in Firefox ESR 91.3 — MozillaVendor Advisory
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https://www.debian.org/security/2022/dsa-5034
Debian -- Security Information -- DSA-5034-1 thunderbirdThird Party Advisory
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https://security.gentoo.org/glsa/202208-14
Mozilla Thunderbird: Multiple Vulnerabilities (GLSA 202208-14) — Gentoo securityThird Party Advisory
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https://www.mozilla.org/security/advisories/mfsa2021-48/
Security Vulnerabilities fixed in Firefox 94 — MozillaVendor Advisory
Products affected by CVE-2021-38507
- cpe:2.3:o:debian:debian_linux:9.0:*:*:*:*:*:*:*
- cpe:2.3:o:debian:debian_linux:10.0:*:*:*:*:*:*:*
- cpe:2.3:o:debian:debian_linux:11.0:*:*:*:*:*:*:*
- cpe:2.3:a:mozilla:firefox:*:*:*:*:*:*:*:*
- cpe:2.3:a:mozilla:thunderbird:*:*:*:*:*:*:*:*
- cpe:2.3:a:mozilla:firefox_esr:*:*:*:*:*:*:*:*