CVE-2020-35861: An issue was discovered in the bumpalo crate before 3.2.1 for Rust

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HIGH 7.5REMOTEUPGRADE

CVE-2020-35861 is a high-severity flaw (CVSS 7.5) affecting bumpalo. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

An issue was discovered in the bumpalo crate before 3.2.1 for Rust. The realloc feature allows the reading of unknown memory. Attackers can potentially read cryptographic keys.

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	1.5% (top 26%)
CISA exploited list	No
Weakness	CWE-125
Published	2020-12-31
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: bumpalo project

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

Am I affected?

Timeline

2020-12-31 10:15 UTCPublished CVE record published
2026-06-17 03:14 UTCUpdated Record last modified

bumpalo project bumpalo UPGRADE

Affected: >= 3.0.0 and < 3.2.1

Fixed in: 3.2.1

Safe to downgrade to: a release before 3.0.0

1. Check installed version

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

2. UPGRADE to 3.2.1 (Debian / Ubuntu)

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

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade bumpalo

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 3.0.0 (Debian / Ubuntu)

apt-cache madison bumpalo sudo apt install bumpalo=<VERSION_BEFORE_3.0.0> sudo apt-mark hold bumpalo

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

dnf --showduplicates list bumpalo sudo dnf downgrade bumpalo-<VERSION_BEFORE_3.0.0> sudo dnf versionlock add bumpalo

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-2020-35861?

bumpalo: upgrade to 3.2.1. Exact commands for each OS are on this page.

Is CVE-2020-35861 being exploited?

CVE-2020-35861 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-2020-35861 affect?

CVE-2020-35861 affects bumpalo. Severity is high (CVSS 7.5). An issue was discovered in the bumpalo crate before 3.2.1 for Rust. The realloc feature allows the reading of unknown memory. Attackers can potentially read cryptographic keys.

How urgent is CVE-2020-35861?

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

References

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