CVE-2011-0493: Tor before 0.2.1.29 and 0.2.2.x before 0.2.2.21-alpha might allow remote attackers to cause a denial of servic

Q: How do I fix CVE-2011-0493?

tor: upgrade to newer than 0.2.1.28. Exact commands for each OS are on this page.

Q: Is CVE-2011-0493 being exploited?

CVE-2011-0493 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-2011-0493 affect?

CVE-2011-0493 affects tor. Severity is medium (CVSS 5.0). Tor before 0.2.1.29 and 0.2.2.x before 0.2.2.21-alpha might allow remote attackers to cause a denial of service (assertion failure and daemon exit) via vectors related to malformed router caches and improper handling of integer values.

Q: How urgent is CVE-2011-0493?

Priority 39/100. No elevated risk signals yet.

Routine

MEDIUM 5.0UPGRADE

CVE-2011-0493 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.

Tor before 0.2.1.29 and 0.2.2.x before 0.2.2.21-alpha might allow remote attackers to cause a denial of service (assertion failure and daemon exit) via vectors related to malformed router caches and improper handling of integer values.

Why this priority

No elevated risk signals yet

A fixed release or distro patch exists.

Risk facts

CVSS score	5.0 (Medium)
EPSS exploit chance	2.5% (top 15%)
CISA exploited list	No
Weakness	CWE-189
Published	2011-01-19
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

2011-01-19 12:00 UTCPublished CVE record published
2026-06-16 23:27 UTCUpdated Record last modified

tor tor UPGRADE

Affected: <= 0.2.1.28 · 0.0.2 · 0.0.2_pre13 · 0.0.2_pre14 · 0.0.2_pre15 · 0.0.2_pre16 · 0.0.2_pre17 · 0.0.2_pre18

Fixed in: newer than 0.2.1.28

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 0.2.1.28 (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-2011-0493?

tor: upgrade to newer than 0.2.1.28. Exact commands for each OS are on this page.

Is CVE-2011-0493 being exploited?

CVE-2011-0493 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-2011-0493 affect?

CVE-2011-0493 affects tor. Severity is medium (CVSS 5.0). Tor before 0.2.1.29 and 0.2.2.x before 0.2.2.21-alpha might allow remote attackers to cause a denial of service (assertion failure and daemon exit) via vectors related to malformed router caches and improper handling of integer values.

How urgent is CVE-2011-0493?

Priority 39/100. 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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