Description
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.
Analysis and contextual insights are available on OpenCVE Cloud.
Remediation
No vendor fix or workaround currently provided.
Additional remediation guidance may be available on OpenCVE Cloud.
Tracking
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Advisories
| Source | ID | Title |
|---|---|---|
Debian DLA |
DLA-2863-1 | firefox-esr security update |
Debian DLA |
DLA-2874-1 | thunderbird security update |
Debian DSA |
DSA-5026-1 | firefox-esr security update |
Debian DSA |
DSA-5034-1 | thunderbird security update |
EUVD |
EUVD-2021-24959 | 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. |
Ubuntu USN |
USN-5131-1 | Firefox vulnerabilities |
Ubuntu USN |
USN-5152-1 | Thunderbird vulnerabilities |
Ubuntu USN |
USN-5248-1 | Thunderbird vulnerabilities |
References
History
No history.
Status: PUBLISHED
Assigner: mozilla
Published:
Updated: 2024-08-04T01:44:23.527Z
Reserved: 2021-08-10T00:00:00.000Z
Link: CVE-2021-38507
No data.
Status : Modified
Published: 2021-12-08T22:15:08.947
Modified: 2024-11-21T06:17:16.447
Link: CVE-2021-38507
OpenCVE Enrichment
No data.
Debian DLA
Debian DSA
EUVD
Ubuntu USN