CVE-2011-4973: Authentication bypass vulnerability in mod_nss 1.0.8 allows remote attackers to assume the identity of a valid

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CRITICAL 9.8REMOTEDOWNGRADE

CVE-2011-4973 is a critical-severity flaw (CVSS 9.8) affecting mod nss. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Authentication bypass vulnerability in mod_nss 1.0.8 allows remote attackers to assume the identity of a valid user by using their certificate and entering 'password' as the password.

Why this priority

Critical severity
Remotely exploitable, no login, no user action

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

Risk facts

CVSS score	9.8 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	1.0% (top 37%)
CISA exploited list	No
Weakness	CWE-287
Published	2018-02-15
Last modified	2026-06-16

Publisher (CNA): Red Hat, Inc. · Vendor: mod nss project

Last updated 2026-06-16 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2018-02-15 21:29 UTCPublished CVE record published
2026-06-16 23:35 UTCUpdated Record last modified

mod nss project mod nss DOWNGRADE

Affected: 1.0.8

Fixed in: no fixed release known

Safe to downgrade to: a release before 1.0.8

1. Check installed version

apt-cache policy mod-nss || rpm -q mod-nss || mod-nss --version

2. No fixed release: DOWNGRADE to a release before 1.0.8 (Debian / Ubuntu)

apt-cache madison mod-nss sudo apt install mod-nss=<VERSION_BEFORE_1.0.8> sudo apt-mark hold mod-nss

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

dnf --showduplicates list mod-nss sudo dnf downgrade mod-nss-<VERSION_BEFORE_1.0.8> sudo dnf versionlock add mod-nss

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-2011-4973?

mod nss: downgrade or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2011-4973 being exploited?

CVE-2011-4973 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-2011-4973 affect?

CVE-2011-4973 affects mod nss. Severity is critical (CVSS 9.8). Authentication bypass vulnerability in mod_nss 1.0.8 allows remote attackers to assume the identity of a valid user by using their certificate and entering 'password' as the password.

How urgent is CVE-2011-4973?

Priority 55/100. Critical severity; Remotely exploitable, no login, no user action

Related CVEs

CVE-2015-5244 CRITICAL 9.8 UPGRADE The NSSCipherSuite option with ciphersuites enabled in mod_nss before 1.0.12 allows remote attackers to bypass
CVE-2015-3277 HIGH 7.5 UPGRADE The mod_nss module before 1.0.11 in Fedora allows remote attackers to obtain cipher lists due to incorrect par

References

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