CVE-2021-31162: In the standard library in Rust before 1.52.0, a double free can occur in the Vec::from_iter function if freei

This week

CRITICAL 9.8REMOTEUPGRADEMITIGATE

CVE-2021-31162 is a critical-severity flaw (CVSS 9.8) affecting rust, fedora. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

In the standard library in Rust before 1.52.0, a double free can occur in the Vec::from_iter function if freeing the element panics.

Why this priority

Critical severity
Public exploit reference
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	2.9% (top 13%)
CISA exploited list	No
Weakness	CWE-415
Published	2021-04-14
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: fedoraproject · rust-lang

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

Am I affected?

Timeline

2021-04-14 07:15 UTCPublished CVE record published
2026-06-17 03:51 UTCUpdated Record last modified

rust-lang rust UPGRADE

Affected: >= 1.48.0 and < 1.52.0

Fixed in: 1.52.0

Safe to downgrade to: a release before 1.48.0

1. Check installed version

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

2. UPGRADE to 1.52.0 (Debian / Ubuntu)

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

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade rust

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 1.48.0 (Debian / Ubuntu)

apt-cache madison rust sudo apt install rust=<VERSION_BEFORE_1.48.0> sudo apt-mark hold rust

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

dnf --showduplicates list rust sudo dnf downgrade rust-<VERSION_BEFORE_1.48.0> sudo dnf versionlock add rust

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.

fedoraproject fedora MITIGATE

Affected: 32 · 33 · 34

Fixed in: no fixed release known

Safe to downgrade to: a release before 32

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

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-2021-31162?

rust: upgrade to 1.52.0; fedora: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2021-31162 being exploited?

CVE-2021-31162 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-2021-31162 affect?

CVE-2021-31162 affects rust, fedora. Severity is critical (CVSS 9.8). In the standard library in Rust before 1.52.0, a double free can occur in the Vec::from_iter function if freeing the element panics.

How urgent is CVE-2021-31162?

Priority 66/100. Critical severity; Public exploit reference; Remotely exploitable, no login, no user action

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References

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