CVE-2020-26950 Use after free in Firefox
High 8.8
Published
Updated
Check this codebase for CVE-2020-26950 and fix it if it is affected.
What it is: CVE-2020-26950 is a high-severity use after free vulnerability in Mozilla Firefox, published on 9 Dec 2020. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2020-26950 exists.
Affected product: Mozilla Firefox. No package-level version data is available, so check the vendor advisory linked from the reference page.
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-2020-26950/ (Markdown: https://insights.sbomify.com/CVE-2020-26950/index.md)
A use-after-free vulnerability in Firefox allows attackers to execute arbitrary code via crafted web content.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- Available
What is CVE-2020-26950?
CVE-2020-26950 is a high-severity use after free vulnerability in Mozilla Firefox, published on 9 Dec 2020. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Official description
In certain circumstances, the MCallGetProperty opcode can be emitted with unmet assumptions resulting in an exploitable use-after-free condition. This vulnerability affects Firefox < 82.0.3, Firefox ESR < 78.4.1, and Thunderbird < 78.4.2.
Weakness: CWE-416
Which versions are affected by CVE-2020-26950?
It affects 3 products.
Linux distribution packages (40)
firefox Red Hat:enterprise_linux:6::client | All versions | 0:78.4.1-1.el6_10 |
firefox-debuginfo Red Hat:enterprise_linux:6::client | All versions | 0:78.4.1-1.el6_10 |
thunderbird Red Hat:enterprise_linux:6::client | All versions | 0:78.4.3-1.el6_10 |
thunderbird-debuginfo Red Hat:enterprise_linux:6::client | All versions | 0:78.4.3-1.el6_10 |
firefox Red Hat:enterprise_linux:6::computenode | All versions | 0:78.4.1-1.el6_10 |
firefox-debuginfo Red Hat:enterprise_linux:6::computenode | All versions | 0:78.4.1-1.el6_10 |
firefox Red Hat:enterprise_linux:6::server | All versions | 0:78.4.1-1.el6_10 |
firefox-debuginfo Red Hat:enterprise_linux:6::server | All versions | 0:78.4.1-1.el6_10 |
thunderbird Red Hat:enterprise_linux:6::server | All versions | 0:78.4.3-1.el6_10 |
thunderbird-debuginfo Red Hat:enterprise_linux:6::server | All versions | 0:78.4.3-1.el6_10 |
firefox Red Hat:enterprise_linux:6::workstation | All versions | 0:78.4.1-1.el6_10 |
firefox-debuginfo Red Hat:enterprise_linux:6::workstation | All versions | 0:78.4.1-1.el6_10 |
thunderbird Red Hat:enterprise_linux:6::workstation | All versions | 0:78.4.3-1.el6_10 |
thunderbird-debuginfo Red Hat:enterprise_linux:6::workstation | All versions | 0:78.4.3-1.el6_10 |
firefox Red Hat:enterprise_linux:7::client | All versions | 0:78.4.1-1.el7_9 |
firefox-debuginfo Red Hat:enterprise_linux:7::client | All versions | 0:78.4.1-1.el7_9 |
thunderbird Red Hat:enterprise_linux:7::client | All versions | 0:78.4.3-1.el7_9 |
thunderbird-debuginfo Red Hat:enterprise_linux:7::client | All versions | 0:78.4.3-1.el7_9 |
firefox Red Hat:enterprise_linux:7::server | All versions | 0:78.4.1-1.el7_9 |
firefox-debuginfo Red Hat:enterprise_linux:7::server | All versions | 0:78.4.1-1.el7_9 |
thunderbird Red Hat:enterprise_linux:7::server | All versions | 0:78.4.3-1.el7_9 |
thunderbird-debuginfo Red Hat:enterprise_linux:7::server | All versions | 0:78.4.3-1.el7_9 |
firefox Red Hat:enterprise_linux:7::workstation | All versions | 0:78.4.1-1.el7_9 |
firefox-debuginfo Red Hat:enterprise_linux:7::workstation | All versions | 0:78.4.1-1.el7_9 |
thunderbird Red Hat:enterprise_linux:7::workstation | All versions | 0:78.4.3-1.el7_9 |
thunderbird-debuginfo Red Hat:enterprise_linux:7::workstation | All versions | 0:78.4.3-1.el7_9 |
firefox Red Hat:enterprise_linux:8::appstream | All versions | 0:78.4.1-1.el8_3 |
firefox-debuginfo Red Hat:enterprise_linux:8::appstream | All versions | 0:78.4.1-1.el8_3 |
firefox-debugsource Red Hat:enterprise_linux:8::appstream | All versions | 0:78.4.1-1.el8_3 |
thunderbird Red Hat:enterprise_linux:8::appstream | All versions | 0:78.4.3-1.el8_3 |
thunderbird-debuginfo Red Hat:enterprise_linux:8::appstream | All versions | 0:78.4.3-1.el8_3 |
thunderbird-debugsource Red Hat:enterprise_linux:8::appstream | All versions | 0:78.4.3-1.el8_3 |
firefox Red Hat:rhel_e4s:8.0::appstream | All versions | 0:78.4.1-1.el8_0 |
firefox-debuginfo Red Hat:rhel_e4s:8.0::appstream | All versions | 0:78.4.1-1.el8_0 |
firefox-debugsource Red Hat:rhel_e4s:8.0::appstream | All versions | 0:78.4.1-1.el8_0 |
thunderbird Red Hat:rhel_e4s:8.0::appstream | All versions | 0:78.4.3-1.el8_0 |
thunderbird-debuginfo Red Hat:rhel_e4s:8.0::appstream | All versions | 0:78.4.3-1.el8_0 |
thunderbird-debugsource Red Hat:rhel_e4s:8.0::appstream | All versions | 0:78.4.3-1.el8_0 |
firefox Red Hat:rhel_eus:8.1::appstream | All versions | 0:78.4.1-1.el8_1 |
firefox-debuginfo Red Hat:rhel_eus:8.1::appstream | All versions | 0:78.4.1-1.el8_1 |
Products include Mozilla Firefox, Mozilla Firefox Esr, Mozilla Thunderbird.
How do I fix CVE-2020-26950?
Upgrade to a fixed version.
Upgrade to the fixed version. These bugs are found with fuzzing and sanitisers and avoided by memory-safe languages. More about Use after free.
Is CVE-2020-26950 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2020-26950 exists.
Public exploit code: 1 Metasploit module.
Other vulnerabilities in Mozilla Firefox
Sources
Also known as DEBIAN-CVE-2020-26950, DLA-2448-1, DLA-2449-1, DSA-4788-1, DSA-4790-1, GHSA-cp22-2989-32j9 and 26 more.