Mozilla Firefox/Firefox ESR/Thunderbird HTTP/2 Opportunistic Encryption cleartext transmission

CVSS Meta Temp Score
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CTI Interest Score
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3.0$0-$5k0.00

Summaryinfo

A vulnerability classified as problematic has been found in Mozilla Firefox, Firefox ESR and Thunderbird. This issue affects some unknown processing of the component HTTP2 Opportunistic Encryption. Performing a manipulation results in cleartext transmission. This vulnerability is identified as CVE-2021-38507. The attack can be initiated remotely. There is not any exploit available. It is recommended to upgrade the affected component.

Detailsinfo

A vulnerability, which was classified as problematic, was found in Mozilla Firefox, Firefox ESR and Thunderbird (Web Browser) (version now known). This affects some unknown processing of the component HTTP2 Opportunistic Encryption. The manipulation with an unknown input leads to a cleartext transmission vulnerability. CWE is classifying the issue as CWE-319. The product transmits sensitive or security-critical data in cleartext in a communication channel that can be sniffed by unauthorized actors. This is going to have an impact on confidentiality.

The weakness was released 12/09/2021. It is possible to read the advisory at mozilla.org. This vulnerability is uniquely identified as CVE-2021-38507 since 08/10/2021. It demands that the victim is doing some kind of user interaction. The technical details are unknown and an exploit is not publicly available. The attack technique deployed by this issue is T1040 according to MITRE ATT&CK.

The vulnerability scanner Nessus provides a plugin with the ID 249869 (Linux Distros Unpatched Vulnerability : CVE-2021-38507), which helps to determine the existence of the flaw in a target environment.

Upgrading eliminates this vulnerability.

The vulnerability is also documented in the vulnerability database at Tenable (249869). Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.

Productinfo

Type

Vendor

Name

License

Website

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔍
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 3.1
VulDB Meta Temp Score: 3.0

VulDB Base Score: 3.1
VulDB Temp Score: 3.0
VulDB Vector: 🔍
VulDB Reliability: 🔍

CVSSv2info

AVACAuCIA
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VectorComplexityAuthenticationConfidentialityIntegrityAvailability
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VulDB Base Score: 🔍
VulDB Temp Score: 🔍
VulDB Reliability: 🔍

Exploitinginfo

Class: Cleartext transmission
CWE: CWE-319 / CWE-310
CAPEC: 🔍
ATT&CK: 🔍

Physical: No
Local: No
Remote: Yes

Availability: 🔍
Status: Not defined

EPSS Score: 🔍
EPSS Percentile: 🔍

Price Prediction: 🔍
Current Price Estimation: 🔍

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Nessus ID: 249869
Nessus Name: Linux Distros Unpatched Vulnerability : CVE-2021-38507

Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍

Countermeasuresinfo

Recommended: Upgrade
Status: 🔍

0-Day Time: 🔍

Timelineinfo

08/10/2021 🔍
12/09/2021 +121 days 🔍
12/09/2021 +0 days 🔍
08/18/2025 +1348 days 🔍

Sourcesinfo

Vendor: mozilla.org
Product: mozilla.org

Advisory: mozilla.org
Status: Confirmed

CVE: CVE-2021-38507 (🔍)
GCVE (CVE): GCVE-0-2021-38507
GCVE (VulDB): GCVE-100-187851

Entryinfo

Created: 12/09/2021 08:45
Updated: 08/18/2025 05:14
Changes: 12/09/2021 08:45 (38), 12/11/2021 23:22 (1), 08/18/2025 05:14 (16)
Complete: 🔍
Cache ID: 216::103

Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.

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