# CVE-2021-43527: Memory corruption in NSS

> Heap overflow in NSS allows code execution when processing malicious DER-encoded signatures in email or document viewers.

- **Severity:** Critical 9.8 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 8 Dec 2021
- **Updated:** 4 Aug 2024
- **Also known as:** ALPINE-CVE-2021-43527, ALSA-2021:4903, AZL-7024, CLSA-2021-1638804170, CLSA-2021-1639578644, CLSA-2021-1640002354, CLSA-2022-1645466754, DEBIAN-CVE-2021-43527, DLA-2836-1, DSA-5016-1, GHSA-7hfm-39v6-v3p5, MGASA-2021-0534, OESA-2022-1492, RHSA-2021:4903, RHSA-2021:4904, RHSA-2021:4907, RHSA-2021:4909, RHSA-2021:4919, RHSA-2021:4932, RHSA-2021:4933, RHSA-2021:4946, RHSA-2021:4953, RHSA-2021:4954, RHSA-2021:4969, RHSA-2021:4994, RHSA-2021:5006, RLSA-2021:4903, SUSE-SU-2021:14858-1, SUSE-SU-2021:3934-1, SUSE-SU-2021:3939-1, SUSE-SU-2022:2536-1, UBUNTU-CVE-2021-43527, USN-5168-1, USN-5168-2, USN-5168-3, USN-5168-4, openSUSE-SU-2021:3934-1, openSUSE-SU-2024:11663-1

## What is CVE-2021-43527?

CVE-2021-43527 is a critical memory corruption vulnerability in Netapp Cloud Backup, published on 8 Dec 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

NSS (Network Security Services) versions prior to 3.73 or 3.68.1 ESR are vulnerable to a heap overflow when handling DER-encoded DSA or RSA-PSS signatures. Applications using NSS for handling signatures encoded within CMS, S/MIME, PKCS \#7, or PKCS \#12 are likely to be impacted. Applications using NSS for certificate validation or other TLS, X.509, OCSP or CRL functionality may be impacted, depending on how they configure NSS. *Note: This vulnerability does NOT impact Mozilla Firefox.* However, email clients and PDF viewers that use NSS for signature verification, such as Thunderbird, LibreOffice, Evolution and Evince are believed to be impacted. This vulnerability affects NSS < 3.73 and NSS < 3.68.1.

Weakness: CWE-787 (Out-of-bounds Write)

## Which versions are affected by CVE-2021-43527?

It affects 10 products.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `nss` | AlmaLinux:8 | All versions | 3.67.0-7.el8_5 |
| `nss-devel` | AlmaLinux:8 | All versions | 3.67.0-7.el8_5 |
| `nss-softokn` | AlmaLinux:8 | All versions | 3.67.0-7.el8_5 |
| `nss-softokn-devel` | AlmaLinux:8 | All versions | 3.67.0-7.el8_5 |
| `nss-softokn-freebl` | AlmaLinux:8 | All versions | 3.67.0-7.el8_5 |
| `nss-softokn-freebl-devel` | AlmaLinux:8 | All versions | 3.67.0-7.el8_5 |
| `nss-sysinit` | AlmaLinux:8 | All versions | 3.67.0-7.el8_5 |
| `nss-tools` | AlmaLinux:8 | All versions | 3.67.0-7.el8_5 |
| `nss-util` | AlmaLinux:8 | All versions | 3.67.0-7.el8_5 |
| `nss-util-devel` | AlmaLinux:8 | All versions | 3.67.0-7.el8_5 |
| `nss` | Red Hat:enterprise_linux:7::client | All versions | 0:3.67.0-4.el7_9 |
| `nss-debuginfo` | Red Hat:enterprise_linux:7::client | All versions | 0:3.67.0-4.el7_9 |
| `nss-devel` | Red Hat:enterprise_linux:7::client | All versions | 0:3.67.0-4.el7_9 |
| `nss-pkcs11-devel` | Red Hat:enterprise_linux:7::client | All versions | 0:3.67.0-4.el7_9 |
| `nss-sysinit` | Red Hat:enterprise_linux:7::client | All versions | 0:3.67.0-4.el7_9 |
| `nss-tools` | Red Hat:enterprise_linux:7::client | All versions | 0:3.67.0-4.el7_9 |
| `nss-debuginfo` | Red Hat:enterprise_linux:7::computenode | All versions | 0:3.67.0-4.el7_9 |
| `nss-devel` | Red Hat:enterprise_linux:7::computenode | All versions | 0:3.67.0-4.el7_9 |
| `nss-pkcs11-devel` | Red Hat:enterprise_linux:7::computenode | All versions | 0:3.67.0-4.el7_9 |
| `nss` | Red Hat:enterprise_linux:7::server | All versions | 0:3.67.0-4.el7_9 |
| `nss-debuginfo` | Red Hat:enterprise_linux:7::server | All versions | 0:3.67.0-4.el7_9 |
| `nss-devel` | Red Hat:enterprise_linux:7::server | All versions | 0:3.67.0-4.el7_9 |
| `nss-pkcs11-devel` | Red Hat:enterprise_linux:7::server | All versions | 0:3.67.0-4.el7_9 |
| `nss-sysinit` | Red Hat:enterprise_linux:7::server | All versions | 0:3.67.0-4.el7_9 |
| `nss-tools` | Red Hat:enterprise_linux:7::server | All versions | 0:3.67.0-4.el7_9 |
| `nss` | Red Hat:enterprise_linux:7::workstation | All versions | 0:3.67.0-4.el7_9 |
| `nss-debuginfo` | Red Hat:enterprise_linux:7::workstation | All versions | 0:3.67.0-4.el7_9 |
| `nss-devel` | Red Hat:enterprise_linux:7::workstation | All versions | 0:3.67.0-4.el7_9 |
| `nss-pkcs11-devel` | Red Hat:enterprise_linux:7::workstation | All versions | 0:3.67.0-4.el7_9 |
| `nss-sysinit` | Red Hat:enterprise_linux:7::workstation | All versions | 0:3.67.0-4.el7_9 |
| `nss-tools` | Red Hat:enterprise_linux:7::workstation | All versions | 0:3.67.0-4.el7_9 |
| `nss` | Red Hat:enterprise_linux:8::appstream | All versions | 0:3.67.0-7.el8_5 |
| `nss-debuginfo` | Red Hat:enterprise_linux:8::appstream | All versions | 0:3.67.0-7.el8_5 |
| `nss-debugsource` | Red Hat:enterprise_linux:8::appstream | All versions | 0:3.67.0-7.el8_5 |
| `nss-devel` | Red Hat:enterprise_linux:8::appstream | All versions | 0:3.67.0-7.el8_5 |
| `nss-softokn` | Red Hat:enterprise_linux:8::appstream | All versions | 0:3.67.0-7.el8_5 |
| `nss-softokn-debuginfo` | Red Hat:enterprise_linux:8::appstream | All versions | 0:3.67.0-7.el8_5 |
| `nss-softokn-devel` | Red Hat:enterprise_linux:8::appstream | All versions | 0:3.67.0-7.el8_5 |
| `nss-softokn-freebl` | Red Hat:enterprise_linux:8::appstream | All versions | 0:3.67.0-7.el8_5 |
| `nss-softokn-freebl-debuginfo` | Red Hat:enterprise_linux:8::appstream | All versions | 0:3.67.0-7.el8_5 |

Products: Mozilla Nss, Mozilla Nss Esr, Netapp Cloud Backup, Netapp E-Series Santricity Os Controller, Oracle Communications Cloud Native Core Binding Support Function, Oracle Communications Cloud Native Core Network Repository Function, Oracle Communications Cloud Native Core Network Slice Selection Function, Oracle Communications Policy Management, Starwindsoftware Starwind San \& Nas, Starwindsoftware Starwind Virtual San.

## How do I fix CVE-2021-43527?

Upgrade to a fixed version.

## Is CVE-2021-43527 being exploited?

There is no known exploitation of CVE-2021-43527 in the wild and no public exploit code.

## Other vulnerabilities in Netapp Cloud Backup

- [CVE-2020-12403](https://insights.sbomify.com/CVE-2020-12403/): Memory corruption in nss (critical 9.1)
- [CVE-2023-4421](https://insights.sbomify.com/CVE-2023-4421/): Information disclosure in NSS (medium 6.5)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-43527 and fix it if it is affected.

What it is: CVE-2021-43527 is a critical memory corruption vulnerability in Netapp Cloud Backup, published on 8 Dec 2021. 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-2021-43527 in the wild and no public exploit code.

Affected product: Netapp Cloud Backup. 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-2021-43527/ (Markdown: https://insights.sbomify.com/CVE-2021-43527/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-43527
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-43527
- OSV: https://osv.dev/vulnerability/CVE-2021-43527

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-43527/
Summaries are generated and may contain mistakes; the official description above is the record.