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Vulnerability record · CVE-2011-0491 · published 19 January 2011

CVE-2011-0491: Tor improper input validation vulnerability

Tor · Tor

The tor_realloc function in Tor before 0.2.1.29 and 0.2.2.x before 0.2.2.21-alpha does not validate a certain size value during memory allocation, which might allow remote attackers to cause a denial of service (daemon crash) via unspecified vectors, related to "underflow errors."

5.0 CVSS 2.0 Medium EPSS 2.5% · top 15.8% CWE-20 · Improper input validation
5.0CVSS 2.0 base score
2.5%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
12References
16 Jun 2026Last modified by NVD

Description

The tor_realloc function in Tor before 0.2.1.29 and 0.2.2.x before 0.2.2.21-alpha does not validate a certain size value during memory allocation, which might allow remote attackers to cause a denial of service (daemon crash) via unspecified vectors, related to "underflow errors."

AV:N/AC:L/Au:N/C:N/I:N/A:P

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
http://archives.seul.org/or/announce/Jan-2011/msg00000.html Patch
http://blog.torproject.org/blog/tor-02129-released-security-patches PatchVendor Advisory
http://www.securityfocus.com/bid/45953
https://exchange.xforce.ibmcloud.com/vulnerabilities/64888
https://gitweb.torproject.org/tor.git/blob/refs/heads/release-0.2.2:/ChangeLog Patch
https://trac.torproject.org/projects/tor/ticket/2324
http://archives.seul.org/or/announce/Jan-2011/msg00000.html Patch
http://blog.torproject.org/blog/tor-02129-released-security-patches PatchVendor Advisory
http://www.securityfocus.com/bid/45953
https://exchange.xforce.ibmcloud.com/vulnerabilities/64888
https://gitweb.torproject.org/tor.git/blob/refs/heads/release-0.2.2:/ChangeLog Patch
https://trac.torproject.org/projects/tor/ticket/2324

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Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

10.0CVE-2010-1676Tor memory buffer overflow vulnerabilityHeap-based buffer overflow in Tor before 0.2.1.28 and 0.2.2.x before 0.2.2.20-alpha allows remote attackers to cause a denial of service (daemon cras…EPSS 7.9%10.0CVE-2009-0939Tor vulnerabilityTor before 0.2.0.34 treats incomplete IPv4 addresses as valid, which has unknown impact and attack vectors related to "Spec conformance," as demonstr…EPSS 2.1%10.0CVE-2009-0414Tor vulnerabilityUnspecified vulnerability in Tor before 0.2.0.33 has unspecified impact and remote attack vectors that trigger heap corruption.EPSS 3.0%9.3CVE-2008-5398Tor permissions and access controls vulnerabilityTor before 0.2.0.32 does not properly process the ClientDNSRejectInternalAddresses configuration option in situations where an exit relay issues a po…EPSS 2.0%7.6CVE-2011-2778Tor memory buffer overflow vulnerabilityMultiple heap-based buffer overflows in Tor before 0.2.2.35 allow remote attackers to cause a denial of service (memory corruption) or possibly execu…EPSS 3.8%7.5CVE-2006-3409Tor vulnerabilityInteger overflow in Tor before 0.1.1.20 allows remote attackers to execute arbitrary code via crafted large inputs, which result in a buffer overflow…EPSS 3.7%7.2CVE-2008-5397Tor permissions and access controls vulnerabilityTor before 0.2.0.32 does not properly process the (1) User and (2) Group configuration options, which might allow local users to gain privileges by l…EPSS 0.36%6.8CVE-2011-0427Tor memory buffer overflow vulnerabilityHeap-based buffer overflow in Tor before 0.2.1.29 and 0.2.2.x before 0.2.2.21-alpha allows remote attackers to cause a denial of service (memory corr…EPSS 4.4%

Source: NIST National Vulnerability Database (record CVE-2011-0491), CISA KEV, FIRST EPSS (scores of 2026-09-30). This page is refreshed as NVD updates the record.