CVE-2020-27743: libtac in pam_tacplus through 1.5.1 lacks a check for a failure of RAND_bytes()/RAND_pseudo_bytes()

Q: How do I fix CVE-2020-27743?

pam tacplus: upgrade to newer than 1.5.1. Exact commands for each OS are on this page.

Q: Is CVE-2020-27743 being exploited?

CVE-2020-27743 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2020-27743 affect?

CVE-2020-27743 affects pam tacplus. Severity is critical (CVSS 9.8). libtac in pam_tacplus through 1.5.1 lacks a check for a failure of RAND_bytes()/RAND_pseudo_bytes(). This could lead to use of a non-random/predictable session_id.

Q: How urgent is CVE-2020-27743?

Priority 59/100. Critical severity; Remotely exploitable, no login, no user action

This month

CRITICAL 9.8REMOTEUPGRADE

CVE-2020-27743 is a critical-severity flaw (CVSS 9.8) affecting pam tacplus. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

libtac in pam_tacplus through 1.5.1 lacks a check for a failure of RAND_bytes()/RAND_pseudo_bytes(). This could lead to use of a non-random/predictable session_id.

Why this priority

Critical severity
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	9.8 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	1.7% (top 22%)
CISA exploited list	No
Weakness	CWE-330
Published	2020-10-26
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: pam tacplus project

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

Am I affected?

Timeline

2020-10-26 22:15 UTCPublished CVE record published
2026-06-17 03:09 UTCUpdated Record last modified

pam tacplus project pam tacplus UPGRADE

Affected: <= 1.5.1

Fixed in: newer than 1.5.1

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy pam-tacplus || rpm -q pam-tacplus || pam-tacplus --version

2. UPGRADE to newer than 1.5.1 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade pam-tacplus

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade pam-tacplus

Note

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

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-2020-27743?

pam tacplus: upgrade to newer than 1.5.1. Exact commands for each OS are on this page.

Is CVE-2020-27743 being exploited?

CVE-2020-27743 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-2020-27743 affect?

CVE-2020-27743 affects pam tacplus. Severity is critical (CVSS 9.8). libtac in pam_tacplus through 1.5.1 lacks a check for a failure of RAND_bytes()/RAND_pseudo_bytes(). This could lead to use of a non-random/predictable session_id.

How urgent is CVE-2020-27743?

Priority 59/100. Critical severity; Remotely exploitable, no login, no user action

Related CVEs

CVE-2020-13881 HIGH 7.5 UPGRADE MITIGATE In support.c in pam_tacplus 1.3.8 through 1.5.1, the TACACS+ shared secret gets logged via syslog if the DEBUG
CVE-2016-20014 CRITICAL 9.8 UPGRADE In pam_tacplus.c in pam_tacplus before 1.4.1, pam_sm_acct_mgmt does not zero out the arep data structure.

References

← Back to latest CVEs