CVE-2019-12953: Dropbear 2011.54 through 2018.76 has an inconsistent failure delay that may lead to revealing valid usernames,

This month

MEDIUM 5.3REMOTEUPGRADE

CVE-2019-12953 is a medium-severity flaw (CVSS 5.3) affecting dropbear ssh. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Dropbear 2011.54 through 2018.76 has an inconsistent failure delay that may lead to revealing valid usernames, a different issue than CVE-2018-15599.

Why this priority

Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	5.3 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	1.2% (top 31%)
CISA exploited list	No
Weakness	CWE-203
Published	2020-12-30
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: dropbear ssh project

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

Am I affected?

Timeline

2020-12-30 20:15 UTCPublished CVE record published
2026-06-17 02:15 UTCUpdated Record last modified

dropbear ssh project dropbear ssh UPGRADE

Affected: >= 2011.54 and <= 2018.76

Fixed in: newer than 2018.76

Safe to downgrade to: a release before 2011.54

1. Check installed version

apt-cache policy dropbear-ssh || rpm -q dropbear-ssh || dropbear-ssh --version

2. UPGRADE to newer than 2018.76 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade dropbear-ssh

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade dropbear-ssh

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 2011.54 (Debian / Ubuntu)

apt-cache madison dropbear-ssh sudo apt install dropbear-ssh=<VERSION_BEFORE_2011.54> sudo apt-mark hold dropbear-ssh

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

dnf --showduplicates list dropbear-ssh sudo dnf downgrade dropbear-ssh-<VERSION_BEFORE_2011.54> sudo dnf versionlock add dropbear-ssh

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-2019-12953?

dropbear ssh: upgrade to newer than 2018.76. Exact commands for each OS are on this page.

Is CVE-2019-12953 being exploited?

CVE-2019-12953 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-2019-12953 affect?

CVE-2019-12953 affects dropbear ssh. Severity is medium (CVSS 5.3). Dropbear 2011.54 through 2018.76 has an inconsistent failure delay that may lead to revealing valid usernames, a different issue than CVE-2018-15599.

How urgent is CVE-2019-12953?

Priority 41/100. Remotely exploitable, no login, no user action

Related CVEs

CVE-2021-36369 HIGH 7.5 UPGRADE MITIGATE An issue was discovered in Dropbear through 2020.81
CVE-2020-36254 HIGH 8.1 UPGRADE scp.c in Dropbear before 2020.79 mishandles the filename of

References

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