CVE-2020-29651: A denial of service via regular expression in the py.path.svnwc component of py (aka python-py) through 1.9.0

This month

HIGH 7.5REMOTEUPGRADEMITIGATEDOWNGRADE

CVE-2020-29651 is a high-severity flaw (CVSS 7.5) affecting py, fedora, zfs storage appliance kit. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

A denial of service via regular expression in the py.path.svnwc component of py (aka python-py) through 1.9.0 could be used by attackers to cause a compute-time denial of service attack by supplying malicious input to the blame functionality.

Why this priority

High severity
EPSS top 8%: very likely to be exploited
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	4.7% (top 8%)
CISA exploited list	No
Published	2020-12-09
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: fedoraproject · oracle · pytest

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

Am I affected?

Timeline

2020-12-09 07:15 UTCPublished CVE record published
2026-06-17 03:11 UTCUpdated Record last modified

pytest py UPGRADE

Affected: <= 1.9.0

Fixed in: newer than 1.9.0

Safe to downgrade to: no unaffected older release

1. Check installed version

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

2. UPGRADE to newer than 1.9.0 (Debian / Ubuntu)

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

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade py

Note

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

fedoraproject fedora MITIGATE

Affected: 32 · 33

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.

oracle zfs storage appliance kit DOWNGRADE

Affected: 8.8

Fixed in: no fixed release known

Safe to downgrade to: a release before 8.8

1. Check installed version

apt-cache policy zfs-storage-appliance-kit || rpm -q zfs-storage-appliance-kit || zfs-storage-appliance-kit --version

2. No fixed release: DOWNGRADE to a release before 8.8 (Debian / Ubuntu)

apt-cache madison zfs-storage-appliance-kit sudo apt install zfs-storage-appliance-kit=<VERSION_BEFORE_8.8> sudo apt-mark hold zfs-storage-appliance-kit

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

dnf --showduplicates list zfs-storage-appliance-kit sudo dnf downgrade zfs-storage-appliance-kit-<VERSION_BEFORE_8.8> sudo dnf versionlock add zfs-storage-appliance-kit

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-2020-29651?

py: upgrade to newer than 1.9.0; fedora: mitigate or apply the listed mitigation; zfs storage appliance kit: downgrade or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2020-29651 being exploited?

CVE-2020-29651 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-2020-29651 affect?

CVE-2020-29651 affects py, fedora, zfs storage appliance kit. Severity is high (CVSS 7.5). A denial of service via regular expression in the py.path.svnwc component of py (aka python-py) through 1.9.0 could be used by attackers to cause a compute-time denial of service attack by supplying malicious input to the blame functionalit

How urgent is CVE-2020-29651?

Priority 54/100. High severity; EPSS top 8%: very likely to be exploited; Remotely exploitable, no login, no user action

Software pages

Python vulnerabilities

Related CVEs

CVE-2022-42969 MEDIUM 5.3 UPGRADE The py library through 1.11.0 for Python allows remote attackers to conduct a ReDoS (Regular expression Denial

References

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