CVE-2021-29063: A Regular Expression Denial of Service (ReDOS) vulnerability was discovered in Mpmath v1.0.0 through v1.2.1 wh

This week

HIGH 7.5REMOTEUPGRADEMITIGATE

CVE-2021-29063 is a high-severity flaw (CVSS 7.5) affecting mpmath, fedora. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

A Regular Expression Denial of Service (ReDOS) vulnerability was discovered in Mpmath v1.0.0 through v1.2.1 when the mpmathify function is called.

Why this priority

High severity
EPSS top 9%: very likely to be exploited
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	4.2% (top 9%)
CISA exploited list	No
Weakness	CWE-770
Published	2021-06-21
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: fedoraproject · mpmath

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

Am I affected?

Timeline

2021-06-21 20:15 UTCPublished CVE record published
2026-06-17 03:47 UTCUpdated Record last modified

mpmath mpmath UPGRADE

Affected: >= 1.0.0 and <= 1.2.1

Fixed in: newer than 1.2.1

Safe to downgrade to: a release before 1.0.0

1. Check installed version

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

2. UPGRADE to newer than 1.2.1 (Debian / Ubuntu)

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

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade mpmath

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 mpmath sudo apt install mpmath=<VERSION_BEFORE_1.0.0> sudo apt-mark hold mpmath

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

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

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: 33 · 34 · 35

Fixed in: no fixed release known

Safe to downgrade to: a release before 33

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-2021-29063?

mpmath: upgrade to newer than 1.2.1; fedora: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2021-29063 being exploited?

CVE-2021-29063 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-2021-29063 affect?

CVE-2021-29063 affects mpmath, fedora. Severity is high (CVSS 7.5). A Regular Expression Denial of Service (ReDOS) vulnerability was discovered in Mpmath v1.0.0 through v1.2.1 when the mpmathify function is called.

How urgent is CVE-2021-29063?

Priority 59/100. High severity; EPSS top 9%: very likely to be exploited; Public exploit reference; Remotely exploitable, no login, no user action

References

← Back to latest CVEs