CVE-2020-35711: An issue has been discovered in the arc-swap crate before 0.4.8 (and 1.x before 1.1.0) for Rust

This week

HIGH 7.5REMOTEUPGRADE

CVE-2020-35711 is a high-severity flaw (CVSS 7.5) affecting arc-swap. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

An issue has been discovered in the arc-swap crate before 0.4.8 (and 1.x before 1.1.0) for Rust. Use of arc_swap::access::Map with the Constant test helper (or with a user-supplied implementation of the Access trait) could sometimes lead to dangling references being returned by the map.

Why this priority

High severity
Public exploit reference
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	7.5 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	1.6% (top 24%)
CISA exploited list	No
Published	2020-12-25
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: arc-swap project

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

Am I affected?

Timeline

2020-12-25 23:15 UTCPublished CVE record published
2026-06-17 03:14 UTCUpdated Record last modified

arc-swap project arc-swap UPGRADE

Affected: < 0.4.8 · >= 1.0.0 and < 1.1.0

Fixed in: 0.4.8, 1.1.0

Safe to downgrade to: a release before 1.0.0

1. Check installed version

apt-cache policy arc-swap || rpm -q arc-swap || arc-swap --version

2. UPGRADE to 0.4.8 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade arc-swap

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade arc-swap

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 1.0.0 (Debian / Ubuntu)

apt-cache madison arc-swap sudo apt install arc-swap=<VERSION_BEFORE_1.0.0> sudo apt-mark hold arc-swap

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

dnf --showduplicates list arc-swap sudo dnf downgrade arc-swap-<VERSION_BEFORE_1.0.0> sudo dnf versionlock add arc-swap

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-2020-35711?

arc-swap: upgrade to 0.4.8, 1.1.0. Exact commands for each OS are on this page.

Is CVE-2020-35711 being exploited?

CVE-2020-35711 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-2020-35711 affect?

CVE-2020-35711 affects arc-swap. Severity is high (CVSS 7.5). An issue has been discovered in the arc-swap crate before 0.4.8 (and 1.x before 1.1.0) for Rust. Use of arc_swap::access::Map with the Constant test helper (or with a user-supplied implementation of the Access trait) could sometimes lead to

How urgent is CVE-2020-35711?

Priority 55/100. High severity; Public exploit reference; Remotely exploitable, no login, no user action

References

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