CVE-2020-25657: A flaw was found in all released versions of m2crypto, where they are vulnerable to Bleichenbacher timing atta

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MEDIUM 5.9REMOTEWATCHLISTMITIGATEDOWNGRADEMITIGATE

CVE-2020-25657 is a medium-severity flaw (CVSS 5.9) affecting m2crypto, virtualization, enterprise linux. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

A flaw was found in all released versions of m2crypto, where they are vulnerable to Bleichenbacher timing attacks in the RSA decryption API via the timed processing of valid PKCS#1 v1.5 Ciphertext. The highest threat from this vulnerability is to confidentiality.

Why this priority

Remotely exploitable, no login, no user action
On your watchlist

No fix is published yet: follow the downgrade or mitigation steps.

Risk facts

CVSS score	5.9 (Medium)
Attack vector	Network (remote)
Attack complexity	High
Privileges needed	None
User interaction	None
EPSS exploit chance	1.8% (top 22%)
CISA exploited list	No
Weakness	CWE-385
Published	2021-01-12
Last modified	2026-06-17

Publisher (CNA): Red Hat, Inc. · Vendor: fedoraproject · m2crypto project · redhat

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

Am I affected?

Timeline

2021-01-12 15:15 UTCPublished CVE record published
2026-06-17 03:07 UTCUpdated Record last modified

m2crypto project m2crypto MITIGATE

Affected: all versions

Fixed in: no fixed release known

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy m2crypto || rpm -q m2crypto || m2crypto --version

No fixed or unaffected release known

Apply the vendor mitigation from the advisory, disable the affected feature, or restrict network access.

redhat virtualization DOWNGRADE

Affected: 4.0

Fixed in: no fixed release known

Safe to downgrade to: a release before 4.0

1. Check installed version

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

2. No fixed release: DOWNGRADE to a release before 4.0 (Debian / Ubuntu)

apt-cache madison virtualization sudo apt install virtualization=<VERSION_BEFORE_4.0> sudo apt-mark hold virtualization

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

dnf --showduplicates list virtualization sudo dnf downgrade virtualization-<VERSION_BEFORE_4.0> sudo dnf versionlock add virtualization

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.

redhat enterprise linux MITIGATE

Affected: 6.0 · 7.0

Fixed in: no fixed release known

Safe to downgrade to: a release before 6.0

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.

fedoraproject fedora MITIGATE

Affected: 33

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-2020-25657?

m2crypto: mitigate or apply the listed mitigation; virtualization: downgrade or apply the listed mitigation; enterprise linux: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2020-25657 being exploited?

CVE-2020-25657 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-2020-25657 affect?

CVE-2020-25657 affects m2crypto, virtualization, enterprise linux. Severity is medium (CVSS 5.9). A flaw was found in all released versions of m2crypto, where they are vulnerable to Bleichenbacher timing attacks in the RSA decryption API via the timed processing of valid PKCS#1 v1.5 Ciphertext. The highest threat from this vulnerability

How urgent is CVE-2020-25657?

Priority 50/100. Remotely exploitable, no login, no user action; On your watchlist

References

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