CVE-2009-2417: lib/ssluse.c in cURL and libcurl 7.4 through 7.19.5, when OpenSSL is used, does not properly handle a '\0' cha

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HIGH 7.5WATCHLISTDOWNGRADEDOWNGRADE

CVE-2009-2417 is a high-severity flaw (CVSS 7.5) affecting libcurl, libcurl. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

lib/ssluse.c in cURL and libcurl 7.4 through 7.19.5, when OpenSSL is used, does not properly handle a '\0' character in a domain name in the subject's Common Name (CN) field of an X.509 certificate, which allows man-in-the-middle attackers to spoof arbitrary SSL servers via a crafted certificate issued by a legitimate Certification Authority, a related issue to CVE-2009-2408.

Why this priority

High severity
On your watchlist

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

Risk facts

CVSS score	7.5 (High)
EPSS exploit chance	3.5% (top 11%)
CISA exploited list	No
Weakness	CWE-310
Published	2009-08-14
Last modified	2026-06-16

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

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

Am I affected?

Timeline

2009-08-14 15:16 UTCPublished CVE record published
2026-06-16 23:09 UTCUpdated Record last modified

curl libcurl DOWNGRADE

Affected: 7.4 · 7.4.1 · 7.4.2 · 7.5 · 7.5.1 · 7.5.2 · 7.6 · 7.6.1

Fixed in: no fixed release known

Safe to downgrade to: a release before 7.4

1. Check installed version

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

2. No fixed release: DOWNGRADE to a release before 7.4 (Debian / Ubuntu)

apt-cache madison libcurl sudo apt install libcurl=<VERSION_BEFORE_7.4> sudo apt-mark hold libcurl

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

dnf --showduplicates list libcurl sudo dnf downgrade libcurl-<VERSION_BEFORE_7.4> sudo dnf versionlock add libcurl

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.

libcurl libcurl DOWNGRADE

Affected: 7.12 · 7.12.1 · 7.12.2 · 7.12.3 · 7.13 · 7.13.1 · 7.13.2 · 7.14

Fixed in: no fixed release known

Safe to downgrade to: a release before 7.12

1. Check installed version

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

2. No fixed release: DOWNGRADE to a release before 7.12 (Debian / Ubuntu)

apt-cache madison libcurl sudo apt install libcurl=<VERSION_BEFORE_7.12> sudo apt-mark hold libcurl

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

dnf --showduplicates list libcurl sudo dnf downgrade libcurl-<VERSION_BEFORE_7.12> sudo dnf versionlock add libcurl

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-2009-2417?

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

Is CVE-2009-2417 being exploited?

CVE-2009-2417 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-2009-2417 affect?

CVE-2009-2417 affects libcurl, libcurl. Severity is high (CVSS 7.5). lib/ssluse.c in cURL and libcurl 7.4 through 7.19.5, when OpenSSL is used, does not properly handle a '\0' character in a domain name in the subject's Common Name (CN) field of an X.509 certificate, which allows man-in-the-middle attackers

How urgent is CVE-2009-2417?

Priority 54/100. High severity; On your watchlist

Software pages

OpenSSL vulnerabilities · curl vulnerabilities

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References

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