CVE-2007-4099: Tor before 0.1.2.15 can select a guard node beyond the first listed never-before-connected-to guard node, whic

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MEDIUM 5.8DOWNGRADE

CVE-2007-4099 is a medium-severity flaw (CVSS 5.8) affecting tor. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Tor before 0.1.2.15 can select a guard node beyond the first listed never-before-connected-to guard node, which allows remote attackers with control of certain guard nodes to obtain sensitive information and possibly leverage further attacks.

Why this priority

No elevated risk signals yet

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

Risk facts

CVSS score	5.8 (Medium)
EPSS exploit chance	1.9% (top 20%)
CISA exploited list	No
Published	2007-07-30
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

2007-07-30 21:17 UTCPublished CVE record published
2026-06-16 22:43 UTCUpdated Record last modified

tor tor DOWNGRADE

Affected: 0.1.0.10 · 0.1.0.11 · 0.1.0.12 · 0.1.0.13 · 0.1.0.14 · 0.1.0.18 · 0.1.1.1_alpha · 0.1.1.2_alpha

Fixed in: no fixed release known

Safe to downgrade to: a release before 0.1.0.10

1. Check installed version

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

2. No fixed release: DOWNGRADE to a release before 0.1.0.10 (Debian / Ubuntu)

apt-cache madison tor sudo apt install tor=<VERSION_BEFORE_0.1.0.10> sudo apt-mark hold tor

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

dnf --showduplicates list tor sudo dnf downgrade tor-<VERSION_BEFORE_0.1.0.10> sudo dnf versionlock add tor

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-2007-4099?

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

Is CVE-2007-4099 being exploited?

CVE-2007-4099 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-2007-4099 affect?

CVE-2007-4099 affects tor. Severity is medium (CVSS 5.8). Tor before 0.1.2.15 can select a guard node beyond the first listed never-before-connected-to guard node, which allows remote attackers with control of certain guard nodes to obtain sensitive information and possibly leverage further attack

How urgent is CVE-2007-4099?

Priority 40/100. No elevated risk signals yet.

Related CVEs

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References

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