# RHSA-2021:0993: thunderbird security update

RHSA-2021:0993, released March 25, 2021, fixes 5 CVEs in thunderbird (version 0:78.9.0-3.el8_3). None of them is reported as exploited. Patch Radar priority: High.

- Web page: https://patchblox.com/security/fix/linux/rhsa-2021-0993
- Platform: Linux
- Released: Mar 25, 2021
- Priority: High (Closes CVE-2021-23987, high severity)
- CVEs: 5, exploited: 0, on CISA KEV: 0
- Vendor advisory: https://access.redhat.com/errata/RHSA-2021:0993

## Applies to

| Product | Release | Fixed in |
|---|---|---|
| [thunderbird](https://patchblox.com/security/data/product/linux/thunderbird.md) | RHEL 8 | 0:78.9.0-3.el8_3 |

## CVEs this fix closes

| CVE | Priority | Title | CVSS | EPSS | Exploitation |
|---|---|---|---:|---:|---|
| [CVE-2021-23987](https://patchblox.com/security/data/cve/CVE-2021-23987.md) | High | Firefox ESR and 2 others: Mozilla developers and community members reported memory safety bugs present in Firefox 86 and Firefox… | 8.8 | 0.0142 |  |
| [CVE-2021-23981](https://patchblox.com/security/data/cve/CVE-2021-23981.md) | High | Firefox ESR and 2 others: A texture upload of a Pixel Buffer Object could have confused the WebGL code to skip binding the buffer… | 8.1 | 0.0115 |  |
| [CVE-2021-4127](https://patchblox.com/security/data/cve/CVE-2021-4127.md) | High | Thunderbird: An out of date graphics library (Angle) likely contained vulnerabilities that could potentially be exploited. | 9.8 | 0.0095 |  |
| [CVE-2021-23984](https://patchblox.com/security/data/cve/CVE-2021-23984.md) | Routine | Firefox ESR and 2 others: A malicious extension could have opened a popup window lacking an address bar. | 6.5 | 0.0111 |  |
| [CVE-2021-23982](https://patchblox.com/security/data/cve/CVE-2021-23982.md) | Routine | Firefox ESR and 2 others: Using techniques that built on the slipstream research, a malicious webpage could have scanned both an… | 6.5 | 0.0074 |  |

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Data as of 2026-11-07T12:40:37Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo