CVE-2009-2426: The connection_edge_process_relay_cell_not_open function in src/or/relay.c in Tor 0.2.x before 0.2.0.35 and 0.

Routine

MEDIUM 5.0DOWNGRADE

CVE-2009-2426 is a medium-severity flaw (CVSS 5.0) affecting tor. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

The connection_edge_process_relay_cell_not_open function in src/or/relay.c in Tor 0.2.x before 0.2.0.35 and 0.1.x before 0.1.2.8-beta allows exit relays to have an unspecified impact by causing controllers to accept DNS responses that redirect to an internal IP address via unknown vectors. NOTE: some of these details are obtained from third party information.

Why this priority

No elevated risk signals yet

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

Risk facts

CVSS score	5.0 (Medium)
EPSS exploit chance	1.9% (top 20%)
CISA exploited list	No
Published	2009-07-10
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

2009-07-10 17:30 UTCPublished CVE record published
2026-06-16 23:09 UTCUpdated Record last modified

tor tor DOWNGRADE

Affected: 0.1.0.1 · 0.1.0.2 · 0.1.0.3 · 0.1.0.4 · 0.1.0.5 · 0.1.0.6 · 0.1.0.7 · 0.1.0.8

Fixed in: no fixed release known

Safe to downgrade to: a release before 0.1.0.1

1. Check installed version

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

2. No fixed release: DOWNGRADE to a release before 0.1.0.1 (Debian / Ubuntu)

apt-cache madison tor sudo apt install tor=<VERSION_BEFORE_0.1.0.1> sudo apt-mark hold tor

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

dnf --showduplicates list tor sudo dnf downgrade tor-<VERSION_BEFORE_0.1.0.1> 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-2009-2426?

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

Is CVE-2009-2426 being exploited?

CVE-2009-2426 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-2009-2426 affect?

CVE-2009-2426 affects tor. Severity is medium (CVSS 5.0). The connection_edge_process_relay_cell_not_open function in src/or/relay.c in Tor 0.2.x before 0.2.0.35 and 0.1.x before 0.1.2.8-beta allows exit relays to have an unspecified impact by causing controllers to accept DNS responses that redir

How urgent is CVE-2009-2426?

Priority 37/100. No elevated risk signals yet.

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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