# CVE-2021-21708: UAF due to php_filter_float() failing > A use-after-free vulnerability in PHP's float filter allows attackers to cause crashes or potentially execute arbitrary code via crafted input. - **Severity:** High 8.2 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:L`) - **Exploited in the wild:** Not known - **Login needed:** Not needed - **Attackable:** Over the internet - **Victim action needed:** Not needed - **Fix available:** Yes - **Published:** 27 Feb 2022 - **Updated:** 17 Sep 2024 - **Also known as:** BIT-libphp-2021-21708, BIT-php-2021-21708, BIT-php-min-2021-21708, CLSA-2022-1647550779, CLSA-2022-1647550845, DEBIAN-CVE-2021-21708, GHSA-g9qg-rg7j-whhx, OESA-2022-1581, RHSA-2025:3016, RHSA-2025:3076, SUSE-SU-2022:0654-1, SUSE-SU-2022:0847-1, UBUNTU-CVE-2021-21708, USN-5303-1, openSUSE-SU-2022:0847-1, openSUSE-SU-2024:11854-1, openSUSE-SU-2024:11861-1 ## What is CVE-2021-21708? CVE-2021-21708 is a high-severity use after free vulnerability in Php Php, published on 27 Feb 2022. An attacker can exploit it over the internet without logging in, with no action from the victim. ### Official description In PHP versions 7.4.x below 7.4.28, 8.0.x below 8.0.16, and 8.1.x below 8.1.3, when using filter functions with FILTER_VALIDATE_FLOAT filter and min/max limits, if the filter fails, there is a possibility to trigger use of allocated memory after free, which can result it crashes, and potentially in overwrite of other memory chunks and RCE. This issue affects: code that uses FILTER_VALIDATE_FLOAT with min/max limits. Weakness: CWE-416 (Use After Free) ## Which versions are affected by CVE-2021-21708? 3 open source packages ship an affected version, including libphp, php and php-min. It affects 1 product. | Package | Ecosystem | Affected | Fixed in | | --- | --- | --- | --- | | `libphp` | Bitnami | From 7.4.0 | 7.4.28, 8.0.16, 8.1.3 | | `php` | Bitnami | From 7.4.0 | 7.4.28, 8.0.16, 8.1.3 | | `php-min` | Bitnami | From 7.4.0 | 7.4.28, 8.0.16, 8.1.3 | | `apcu-panel` | Red Hat:rhel_aus:8.4::appstream | All versions | 0:5.1.18-1.module+el8.3.0+6678+b09f589e | | `libzip` | Red Hat:rhel_aus:8.4::appstream | All versions | 0:1.6.1-1.module+el8.3.0+6678+b09f589e | | `libzip-debuginfo` | Red Hat:rhel_aus:8.4::appstream | All versions | 0:1.6.1-1.module+el8.3.0+6678+b09f589e | | `libzip-debugsource` | Red Hat:rhel_aus:8.4::appstream | All versions | 0:1.6.1-1.module+el8.3.0+6678+b09f589e | | `libzip-devel` | Red Hat:rhel_aus:8.4::appstream | All versions | 0:1.6.1-1.module+el8.3.0+6678+b09f589e | | `libzip-tools` | Red Hat:rhel_aus:8.4::appstream | All versions | 0:1.6.1-1.module+el8.3.0+6678+b09f589e | | `libzip-tools-debuginfo` | Red Hat:rhel_aus:8.4::appstream | All versions | 0:1.6.1-1.module+el8.3.0+6678+b09f589e | | `php` | Red Hat:rhel_aus:8.4::appstream | All versions | 0:7.4.6-5.module+el8.4.0+22918+4f86939b.1 | | `php-bcmath` | Red Hat:rhel_aus:8.4::appstream | All versions | 0:7.4.6-5.module+el8.4.0+22918+4f86939b.1 | | `php-bcmath-debuginfo` | Red Hat:rhel_aus:8.4::appstream | All versions | 0:7.4.6-5.module+el8.4.0+22918+4f86939b.1 | | `php-cli` | Red Hat:rhel_aus:8.4::appstream | All versions | 0:7.4.6-5.module+el8.4.0+22918+4f86939b.1 | | `php-cli-debuginfo` | Red Hat:rhel_aus:8.4::appstream | All versions | 0:7.4.6-5.module+el8.4.0+22918+4f86939b.1 | | `php-common` | Red Hat:rhel_aus:8.4::appstream | All versions | 0:7.4.6-5.module+el8.4.0+22918+4f86939b.1 | | `php-common-debuginfo` | Red Hat:rhel_aus:8.4::appstream | All versions | 0:7.4.6-5.module+el8.4.0+22918+4f86939b.1 | | `php-dba` | Red Hat:rhel_aus:8.4::appstream | All versions | 0:7.4.6-5.module+el8.4.0+22918+4f86939b.1 | | `php-dba-debuginfo` | Red Hat:rhel_aus:8.4::appstream | All versions | 0:7.4.6-5.module+el8.4.0+22918+4f86939b.1 | | `php-dbg` | Red Hat:rhel_aus:8.4::appstream | All versions | 0:7.4.6-5.module+el8.4.0+22918+4f86939b.1 | | `php-dbg-debuginfo` | Red Hat:rhel_aus:8.4::appstream | All versions | 0:7.4.6-5.module+el8.4.0+22918+4f86939b.1 | | `php-debuginfo` | Red Hat:rhel_aus:8.4::appstream | All versions | 0:7.4.6-5.module+el8.4.0+22918+4f86939b.1 | | `php-debugsource` | Red Hat:rhel_aus:8.4::appstream | All versions | 0:7.4.6-5.module+el8.4.0+22918+4f86939b.1 | | `php-devel` | Red Hat:rhel_aus:8.4::appstream | All versions | 0:7.4.6-5.module+el8.4.0+22918+4f86939b.1 | | `php-embedded` | Red Hat:rhel_aus:8.4::appstream | All versions | 0:7.4.6-5.module+el8.4.0+22918+4f86939b.1 | | `php-embedded-debuginfo` | Red Hat:rhel_aus:8.4::appstream | All versions | 0:7.4.6-5.module+el8.4.0+22918+4f86939b.1 | | `php-enchant` | Red Hat:rhel_aus:8.4::appstream | All versions | 0:7.4.6-5.module+el8.4.0+22918+4f86939b.1 | | `php-enchant-debuginfo` | Red Hat:rhel_aus:8.4::appstream | All versions | 0:7.4.6-5.module+el8.4.0+22918+4f86939b.1 | | `php-ffi` | Red Hat:rhel_aus:8.4::appstream | All versions | 0:7.4.6-5.module+el8.4.0+22918+4f86939b.1 | | `php-ffi-debuginfo` | Red Hat:rhel_aus:8.4::appstream | All versions | 0:7.4.6-5.module+el8.4.0+22918+4f86939b.1 | | `php-fpm` | Red Hat:rhel_aus:8.4::appstream | All versions | 0:7.4.6-5.module+el8.4.0+22918+4f86939b.1 | | `php-fpm-debuginfo` | Red Hat:rhel_aus:8.4::appstream | All versions | 0:7.4.6-5.module+el8.4.0+22918+4f86939b.1 | | `php-gd` | Red Hat:rhel_aus:8.4::appstream | All versions | 0:7.4.6-5.module+el8.4.0+22918+4f86939b.1 | | `php-gd-debuginfo` | Red Hat:rhel_aus:8.4::appstream | All versions | 0:7.4.6-5.module+el8.4.0+22918+4f86939b.1 | | `php-gmp` | Red Hat:rhel_aus:8.4::appstream | All versions | 0:7.4.6-5.module+el8.4.0+22918+4f86939b.1 | | `php-gmp-debuginfo` | Red Hat:rhel_aus:8.4::appstream | All versions | 0:7.4.6-5.module+el8.4.0+22918+4f86939b.1 | | `php-intl` | Red Hat:rhel_aus:8.4::appstream | All versions | 0:7.4.6-5.module+el8.4.0+22918+4f86939b.1 | | `php-intl-debuginfo` | Red Hat:rhel_aus:8.4::appstream | All versions | 0:7.4.6-5.module+el8.4.0+22918+4f86939b.1 | | `php-json` | Red Hat:rhel_aus:8.4::appstream | All versions | 0:7.4.6-5.module+el8.4.0+22918+4f86939b.1 | | `php-json-debuginfo` | Red Hat:rhel_aus:8.4::appstream | All versions | 0:7.4.6-5.module+el8.4.0+22918+4f86939b.1 | Products: Php Php. ## How do I fix CVE-2021-21708? Upgrade libphp to a fixed version for your release line: 7.4.28, 8.0.16 or 8.1.3. ## Is CVE-2021-21708 being exploited? There is no known exploitation of CVE-2021-21708 in the wild and no public exploit code. ## Other vulnerabilities in Php Php - [CVE-2012-2688](https://insights.sbomify.com/CVE-2012-2688/): Integer overflow in n/a (critical 10.0) - [CVE-2012-2376](https://insights.sbomify.com/CVE-2012-2376/): Memory corruption in n/a (critical 10.0) - [CVE-2011-3268](https://insights.sbomify.com/CVE-2011-3268/): Memory corruption in n/a (critical 10.0) - [CVE-2009-4143](https://insights.sbomify.com/CVE-2009-4143/): Other in n/a (critical 10.0) - [CVE-2008-5557](https://insights.sbomify.com/CVE-2008-5557/): Memory corruption in n/a (critical 10.0) ## Fix prompt for AI coding agents ```text Check this codebase for CVE-2021-21708 and fix it if it is affected. What it is: CVE-2021-21708 is a high-severity use after free vulnerability in Php Php, published on 27 Feb 2022. An attacker can exploit it over the internet without logging in, with no action from the victim. Exploitation: There is no known exploitation of CVE-2021-21708 in the wild and no public exploit code. Affected packages and fixed versions: - libphp (Bitnami): affected from 7.4.0; fixed in 7.4.28, 8.0.16, 8.1.3 - php (Bitnami): affected from 7.4.0; fixed in 7.4.28, 8.0.16, 8.1.3 - php-min (Bitnami): affected from 7.4.0; fixed in 7.4.28, 8.0.16, 8.1.3 Task: 1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies. 2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it. 3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead. 4. Run the tests and summarise what changed and why. 5. If nothing in the project is affected, say so and change nothing. Reference: https://insights.sbomify.com/CVE-2021-21708/ (Markdown: https://insights.sbomify.com/CVE-2021-21708/index.md) ``` ## Sources - CVE record: https://www.cve.org/CVERecord?id=CVE-2021-21708 - NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-21708 - OSV: https://osv.dev/vulnerability/CVE-2021-21708 --- From sbomify Insights: https://insights.sbomify.com/CVE-2021-21708/ Summaries are generated and may contain mistakes; the official description above is the record.