CVE-2009-0939: Tor before 0.2.0.34 treats incomplete IPv4 addresses as valid, which has unknown impact and attack vectors rel

Q: How do I fix CVE-2009-0939?

tor: upgrade to newer than 0.2.0.33. Exact commands for each OS are on this page.

Q: Is CVE-2009-0939 being exploited?

CVE-2009-0939 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-2009-0939 affect?

CVE-2009-0939 affects tor. Severity is high (CVSS 10.0). Tor before 0.2.0.34 treats incomplete IPv4 addresses as valid, which has unknown impact and attack vectors related to "Spec conformance," as demonstrated using 192.168.0.

Q: How urgent is CVE-2009-0939?

Priority 55/100. Critical severity

This month

HIGH 10.0UPGRADE

CVE-2009-0939 is a high-severity flaw (CVSS 10.0) affecting tor. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Tor before 0.2.0.34 treats incomplete IPv4 addresses as valid, which has unknown impact and attack vectors related to "Spec conformance," as demonstrated using 192.168.0.

Why this priority

Critical severity

A fixed release or distro patch exists.

Risk facts

CVSS score	10.0 (High)
EPSS exploit chance	2.1% (top 19%)
CISA exploited list	No
Published	2009-03-18
Last modified	2026-06-16

Publisher (CNA): MITRE · Vendor: tor

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

Am I affected?

Timeline

2009-03-18 02:00 UTCPublished CVE record published
2026-06-16 23:06 UTCUpdated Record last modified

tor tor UPGRADE

Affected: <= 0.2.0.33 · 0.2.0.1 alpha · 0.2.0.2 alpha · 0.2.0.3 alpha · 0.2.0.4 alpha · 0.2.0.5 alpha · 0.2.0.6 alpha · 0.2.0.10 alpha

Fixed in: newer than 0.2.0.33

Safe to downgrade to: no unaffected older release

1. Check installed version

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

2. UPGRADE to newer than 0.2.0.33 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade tor

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade tor

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-2009-0939?

tor: upgrade to newer than 0.2.0.33. Exact commands for each OS are on this page.

Is CVE-2009-0939 being exploited?

CVE-2009-0939 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-2009-0939 affect?

CVE-2009-0939 affects tor. Severity is high (CVSS 10.0). Tor before 0.2.0.34 treats incomplete IPv4 addresses as valid, which has unknown impact and attack vectors related to "Spec conformance," as demonstrated using 192.168.0.

How urgent is CVE-2009-0939?

Priority 55/100. Critical severity

Related CVEs

CVE-2026-44603 LOW 3.7 UPGRADE Tor before 0.4.9.7 has an out-of-bounds read by one byte via a malformed BEGIN cell, aka TROVE-2026-007.
CVE-2026-44597 LOW 3.7 UPGRADE Tor before 0.4.9.7 has an out-of-bounds read when an END, a TRUNCATE, or a TRUNCATED cell lacks a reason in it
CVE-2026-44600 LOW 3.7 UPGRADE Tor before 0.4.9.7 mishandles accounting of the conflux out-of-order queue during the clearing of a queue, aka
CVE-2026-44601 LOW 3.7 UPGRADE Tor before 0.4.9.7, when circuit queue memory pressure exists, can experience a client crash because of a doub
CVE-2026-44602 LOW 3.7 UPGRADE Tor before 0.4.9.7 has a NULL pointer dereference when a CERT cell is received out of order, aka TROVE-2026-00

References

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