# CVE-2021-29955: Firefox ESR and 1 other: A transient execution vulnerability, named Floating Point Value Injection (FPVI) allowed an attacker…

CVE-2021-29955 is fixed in 4 products on 2 platforms, first by firefox 87.0+build3-0ubuntu0.18.04.2, released June 24, 2021. It is not reported as exploited. Patch Radar priority: Routine.

- Web page: https://patchblox.com/security/cve/CVE-2021-29955
- Priority: Routine
- CVSS: 5.3 (Medium)
- EPSS: 0.0148
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Jun 24, 2021
- Vendor advisory: https://nvd.nist.gov/vuln/detail/CVE-2021-29955

## Description

A transient execution vulnerability, named Floating Point Value Injection (FPVI) allowed an attacker to leak arbitrary memory addresses and may have also enabled JIT type confusion attacks. (A related vulnerability, Speculative Code Store Bypass (SCSB), did not affect Firefox.). This vulnerability affects Firefox ESR < 78.9 and Firefox < 87.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Windows apps | Mozilla Firefox ESR (en-US) | 91.0 | [Mozilla Firefox ESR (en-US) 91.0](https://patchblox.com/security/data/fix/windows-app/mozilla.firefox.esr-91.0.md) | Aug 4, 2021 |
| Linux | firefox Ubuntu 18.04.6 LTS (bionic) | 87.0+build3-0ubuntu0.18.04.2 | [firefox 87.0+build3-0ubuntu0.18.04.2](https://patchblox.com/security/data/fix/linux/ubuntu-bionic-firefox-87.0-build3-0ubuntu0.18.04.2.md) | Jun 24, 2021 |
| Linux | firefox-geckodriver Ubuntu 18.04.6 LTS (bionic) | 87.0+build3-0ubuntu0.18.04.2 | [firefox-geckodriver 87.0+build3-0ubuntu0.18.04.2](https://patchblox.com/security/data/fix/linux/ubuntu-bionic-firefox-geckodriver-87.0-build3-0ubuntu0.18.04.2.md) | Jun 24, 2021 |
| Linux | firefox-mozsymbols Ubuntu 18.04.6 LTS (bionic) | 87.0+build3-0ubuntu0.18.04.2 | [firefox-mozsymbols 87.0+build3-0ubuntu0.18.04.2](https://patchblox.com/security/data/fix/linux/ubuntu-bionic-firefox-mozsymbols-87.0-build3-0ubuntu0.18.04.2.md) | Jun 24, 2021 |

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Data as of 2026-11-09T19:38:12Z 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 Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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