# RHSA-2021:0657: thunderbird security update

RHSA-2021:0657, released February 24, 2021, fixes 4 CVEs in thunderbird (version 0:78.8.0-1.el8_3). None of them is reported as exploited. Patch Radar priority: Urgent.

- Web page: https://patchblox.com/security/fix/linux/rhsa-2021-0657
- Platform: Linux
- Released: Feb 24, 2021
- Priority: Urgent (Closes CVE-2021-23978, rated Critical)
- CVEs: 4, exploited: 0, on CISA KEV: 0
- Vendor advisory: https://access.redhat.com/errata/RHSA-2021:0657

## Applies to

| Product | Release | Fixed in |
|---|---|---|
| [thunderbird](https://patchblox.com/security/data/product/linux/thunderbird.md) | RHEL 8 | 0:78.8.0-1.el8_3 |

## CVEs this fix closes

| CVE | Priority | Title | CVSS | EPSS | Exploitation |
|---|---|---|---:|---:|---|
| [CVE-2021-23978](https://patchblox.com/security/data/cve/CVE-2021-23978.md) | Urgent | Firefox ESR and 2 others: Mozilla developers reported memory safety bugs present in Firefox 85 and Firefox ESR 78.7. | 8.8 | 0.0153 |  |
| [CVE-2021-23968](https://patchblox.com/security/data/cve/CVE-2021-23968.md) | Urgent | Firefox ESR and 2 others: If Content Security Policy blocked frame navigation, the full destination of a redirect served in the… | 4.3 | 0.0131 |  |
| [CVE-2021-23969](https://patchblox.com/security/data/cve/CVE-2021-23969.md) | Urgent | Firefox ESR and 2 others: As specified in the W3C Content Security Policy draft, when creating a violation report, "User agents… | 4.3 | 0.0121 |  |
| [CVE-2021-23973](https://patchblox.com/security/data/cve/CVE-2021-23973.md) | Routine | Firefox ESR and 2 others: When trying to load a cross-origin resource in an audio/video context a decoding error may have resulted,… | 6.5 | 0.0137 |  |

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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 Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo