CVE-2011-2940: stunnel 4.40 and 4.41 might allow remote attackers to execute arbitrary code or cause a denial of service (hea

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HIGH 9.3DOWNGRADE

CVE-2011-2940 is a high-severity flaw (CVSS 9.3) affecting stunnel. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

stunnel 4.40 and 4.41 might allow remote attackers to execute arbitrary code or cause a denial of service (heap memory corruption) via unspecified vectors.

Why this priority

Critical severity
EPSS top 7%: very likely to be exploited

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

Risk facts

CVSS score	9.3 (High)
EPSS exploit chance	5.7% (top 7%)
CISA exploited list	No
Weakness	CWE-119
Published	2011-08-25
Last modified	2026-06-16

Publisher (CNA): Red Hat, Inc. · Vendor: stunnel

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

Am I affected?

Timeline

2011-08-25 14:22 UTCPublished CVE record published
2026-06-16 23:32 UTCUpdated Record last modified

stunnel stunnel DOWNGRADE

Affected: 4.40 · 4.41

Fixed in: no fixed release known

Safe to downgrade to: a release before 4.40

1. Check installed version

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

2. No fixed release: DOWNGRADE to a release before 4.40 (Debian / Ubuntu)

apt-cache madison stunnel sudo apt install stunnel=<VERSION_BEFORE_4.40> sudo apt-mark hold stunnel

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

dnf --showduplicates list stunnel sudo dnf downgrade stunnel-<VERSION_BEFORE_4.40> sudo dnf versionlock add stunnel

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-2011-2940?

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

Is CVE-2011-2940 being exploited?

CVE-2011-2940 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-2011-2940 affect?

CVE-2011-2940 affects stunnel. Severity is high (CVSS 9.3). stunnel 4.40 and 4.41 might allow remote attackers to execute arbitrary code or cause a denial of service (heap memory corruption) via unspecified vectors.

How urgent is CVE-2011-2940?

Priority 56/100. Critical severity; EPSS top 7%: very likely to be exploited

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References

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