CVE-2021-43527: NSS (Network Security Services) versions prior to 3.73 or 3.68.1 ESR are vulnerable to a heap overflow when ha

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CRITICAL 9.8REMOTEUPGRADEUPGRADEMITIGATE

CVE-2021-43527 is a critical-severity flaw (CVSS 9.8) affecting nss, nss esr, cloud backup. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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 vulner

Why this priority

Critical severity
EPSS top 3%: very likely to be exploited
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	9.8 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	17.6% (top 3%)
CISA exploited list	No
Weakness	CWE-787
Published	2021-12-08
Last modified	2026-06-17

Publisher (CNA): Mozilla Corporation · Vendor: mozilla · netapp · oracle

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2021-12-08 22:15 UTCPublished CVE record published
2026-06-17 04:11 UTCUpdated Record last modified

mozilla nss UPGRADE

Affected: < 3.73

Fixed in: 3.73

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy nss || rpm -q nss || nss --version

2. UPGRADE to 3.73 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade nss

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade nss

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

mozilla nss esr UPGRADE

Affected: < 3.68.1

Fixed in: 3.68.1

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy nss-esr || rpm -q nss-esr || nss-esr --version

2. UPGRADE to 3.68.1 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade nss-esr

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade nss-esr

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

netapp cloud backup MITIGATE

Affected: all versions

Fixed in: no fixed release known

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy cloud-backup || rpm -q cloud-backup || cloud-backup --version

No fixed or unaffected release known

Apply the vendor mitigation from the advisory, disable the affected feature, or restrict network access.

netapp e-series santricity os controller UPGRADE

Affected: >= 11.0 and <= 11.70.1

Fixed in: newer than 11.70.1

Safe to downgrade to: a release before 11.0

1. Check installed version

apt-cache policy e-series-santricity-os-controller || rpm -q e-series-santricity-os-controller || e-series-santricity-os-controller --version

2. UPGRADE to newer than 11.70.1 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade e-series-santricity-os-controller

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade e-series-santricity-os-controller

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

3. If no update is available yet, DOWNGRADE to a release before 11.0 (Debian / Ubuntu)

apt-cache madison e-series-santricity-os-controller sudo apt install e-series-santricity-os-controller=<VERSION_BEFORE_11.0> sudo apt-mark hold e-series-santricity-os-controller

3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list e-series-santricity-os-controller sudo dnf downgrade e-series-santricity-os-controller-<VERSION_BEFORE_11.0> sudo dnf versionlock add e-series-santricity-os-controller

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

oracle communications cloud native core binding support function DOWNGRADE

Affected: 1.11.0

Fixed in: no fixed release known

Safe to downgrade to: a release before 1.11.0

1. Check installed version

apt-cache policy communications-cloud-native-core-binding-support-function || rpm -q communications-cloud-native-core-binding-support-function || communications-cloud-native-core-binding-support-function --version

2. No fixed release: DOWNGRADE to a release before 1.11.0 (Debian / Ubuntu)

apt-cache madison communications-cloud-native-core-binding-support-function sudo apt install communications-cloud-native-core-binding-support-function=<VERSION_BEFORE_1.11.0> sudo apt-mark hold communications-cloud-native-core-binding-support-function

2. No fixed release: DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list communications-cloud-native-core-binding-support-function sudo dnf downgrade communications-cloud-native-core-binding-support-function-<VERSION_BEFORE_1.11.0> sudo dnf versionlock add communications-cloud-native-core-binding-support-function

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

oracle communications cloud native core network repository function DOWNGRADE

Affected: 1.15.0 · 1.15.1

Fixed in: no fixed release known

Safe to downgrade to: a release before 1.15.0

1. Check installed version

apt-cache policy communications-cloud-native-core-network-repository-function || rpm -q communications-cloud-native-core-network-repository-function || communications-cloud-native-core-network-repository-function --version

2. No fixed release: DOWNGRADE to a release before 1.15.0 (Debian / Ubuntu)

apt-cache madison communications-cloud-native-core-network-repository-function sudo apt install communications-cloud-native-core-network-repository-function=<VERSION_BEFORE_1.15.0> sudo apt-mark hold communications-cloud-native-core-network-repository-function

2. No fixed release: DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list communications-cloud-native-core-network-repository-function sudo dnf downgrade communications-cloud-native-core-network-repository-function-<VERSION_BEFORE_1.15.0> sudo dnf versionlock add communications-cloud-native-core-network-repository-function

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2021-43527?

nss: upgrade to 3.73; nss esr: upgrade to 3.68.1; cloud backup: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2021-43527 being exploited?

CVE-2021-43527 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2021-43527 affect?

CVE-2021-43527 affects nss, nss esr, cloud backup. Severity is critical (CVSS 9.8). 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,

How urgent is CVE-2021-43527?

Priority 64/100. Critical severity; EPSS top 3%: very likely to be exploited; Remotely exploitable, no login, no user action

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References

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