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CVE-2021-30004: In wpa_supplicant and hostapd 2.9, forging attacks may occur because AlgorithmIdentifier parameters are mishan

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MEDIUM 5.3REMOTEDOWNGRADEDOWNGRADE

CVE-2021-30004 is a medium-severity flaw (CVSS 5.3) affecting hostapd, wpa supplicant. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

In wpa_supplicant and hostapd 2.9, forging attacks may occur because AlgorithmIdentifier parameters are mishandled in tls/pkcs1.c and tls/x509v3.c.

Why this priority

  • Remotely exploitable, no login, no user action

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

Risk facts

CVSS score5.3 (Medium)
Attack vectorNetwork (remote)
Attack complexityLow
Privileges neededNone
User interactionNone
EPSS exploit chance1.6% (top 24%)
CISA exploited listNo
WeaknessCWE-20
Published2021-04-02
Last modified2026-07-07
Publisher (CNA): MITRE · Vendor: w1.fi

Share: LinkedIn · X · Reddit

Last updated 2026-07-07 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

w1.fi hostapd DOWNGRADE
Affected: 2.9
Fixed in: no fixed release known
Safe to downgrade to: a release before 2.9
1. Check installed version
apt-cache policy hostapd || rpm -q hostapd || hostapd --version
2. No fixed release: DOWNGRADE to a release before 2.9 (Debian / Ubuntu)
apt-cache madison hostapd sudo apt install hostapd=<VERSION_BEFORE_2.9> sudo apt-mark hold hostapd
2. No fixed release: DOWNGRADE (RHEL / Amazon Linux / Fedora)
dnf --showduplicates list hostapd sudo dnf downgrade hostapd-<VERSION_BEFORE_2.9> sudo dnf versionlock add hostapd
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.
w1.fi wpa supplicant DOWNGRADE
Affected: 2.9
Fixed in: no fixed release known
Safe to downgrade to: a release before 2.9
1. Check installed version
apt-cache policy wpa-supplicant || rpm -q wpa-supplicant || wpa-supplicant --version
2. No fixed release: DOWNGRADE to a release before 2.9 (Debian / Ubuntu)
apt-cache madison wpa-supplicant sudo apt install wpa-supplicant=<VERSION_BEFORE_2.9> sudo apt-mark hold wpa-supplicant
2. No fixed release: DOWNGRADE (RHEL / Amazon Linux / Fedora)
dnf --showduplicates list wpa-supplicant sudo dnf downgrade wpa-supplicant-<VERSION_BEFORE_2.9> sudo dnf versionlock add wpa-supplicant
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-2021-30004?

hostapd: downgrade or apply the listed mitigation; wpa supplicant: downgrade or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2021-30004 being exploited?

CVE-2021-30004 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-2021-30004 affect?

CVE-2021-30004 affects hostapd, wpa supplicant. Severity is medium (CVSS 5.3). In wpa_supplicant and hostapd 2.9, forging attacks may occur because AlgorithmIdentifier parameters are mishandled in tls/pkcs1.c and tls/x509v3.c.

How urgent is CVE-2021-30004?

Priority 43/100. Remotely exploitable, no login, no user action

Related CVEs

References

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