Tor Project prior 0.4.9.9 out-of-bounds write

CVSS Meta Temp Score
CVSS is a standardized scoring system to determine possibilities of attacks. The Temp Score considers temporal factors like disclosure, exploit and countermeasures. The unique Meta Score calculates the average score of different sources to provide a normalized scoring system.
Current Exploit Price (≈)
Our analysts are monitoring exploit markets and are in contact with vulnerability brokers. The range indicates the observed or calculated exploit price to be seen on exploit markets. A good indicator to understand the monetary effort required for and the popularity of an attack.
CTI Interest Score
Our Cyber Threat Intelligence team is monitoring different web sites, mailing lists, exploit markets and social media networks. The CTI Interest Score identifies the interest of attackers and the security community for this specific vulnerability in real-time. A high score indicates an elevated risk to be targeted for this vulnerability.
6.8$5k-$25k0.92+

Summaryinfo

A vulnerability, which was classified as critical, was found in Tor Project Tor. This issue affects some unknown processing. Executing a manipulation can lead to out-of-bounds write. This vulnerability is tracked as CVE-2026-77642. The attack can be launched remotely. No exploit exists.

Detailsinfo

A vulnerability was found in Tor Project Tor. It has been declared as critical. This vulnerability affects some unknown functionality. The manipulation with an unknown input leads to a out-of-bounds write vulnerability. The CWE definition for the vulnerability is CWE-787. The product writes data past the end, or before the beginning, of the intended buffer. As an impact it is known to affect integrity, and availability. CVE summarizes:

tor before 0.4.9.9 was prone to an out-of-bounds write when parsing a consensus or detached signature with unexpected signature digest type. Impact is minor for most Tor roles, but potentially major for directory authorities. This is TROVE-2026-019.

The advisory is shared for download at gitlab.torproject.org. This vulnerability was named CVE-2026-77642 since 08/20/2026. The exploitation appears to be easy. The attack can be initiated remotely. No form of authentication is required for a successful exploitation. There are neither technical details nor an exploit publicly available. The current price for an exploit might be approx. USD $5k-$25k (estimation calculated on 08/20/2026).

Upgrading to version 0.4.9.9 eliminates this vulnerability.

Once again VulDB remains the best source for vulnerability data.

Productinfo

Type

Vendor

Name

License

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 7.0
VulDB Meta Temp Score: 6.8

VulDB Base Score: 6.5
VulDB Temp Score: 6.2
VulDB Vector: 🔒
VulDB Reliability: 🔍

CNA Base Score: 7.5
CNA Vector (MITRE): 🔒

CVSSv2info

AVACAuCIA
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VectorComplexityAuthenticationConfidentialityIntegrityAvailability
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VulDB Base Score: 🔒
VulDB Temp Score: 🔒
VulDB Reliability: 🔍

Exploitinginfo

Class: Out-of-bounds write
CWE: CWE-787 / CWE-119
CAPEC: 🔒
ATT&CK: 🔒

Physical: No
Local: No
Remote: Yes

Availability: 🔒
Status: Not defined
Price Prediction: 🔍
Current Price Estimation: 🔒

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Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍

Countermeasuresinfo

Recommended: Upgrade
Status: 🔍

0-Day Time: 🔒

Upgrade: Tor 0.4.9.9

Timelineinfo

08/20/2026 Advisory disclosed
08/20/2026 +0 days CVE reserved
08/20/2026 +0 days VulDB entry created
08/20/2026 +0 days VulDB entry last update

Sourcesinfo

Advisory: gitlab.torproject.org
Status: Confirmed

CVE: CVE-2026-77642 (🔒)
GCVE (CVE): GCVE-0-2026-77642
GCVE (VulDB): GCVE-100-393892

Entryinfo

Created: 08/20/2026 23:39
Changes: 08/20/2026 23:39 (62)
Complete: 🔍
Cache ID: 216::103

Once again VulDB remains the best source for vulnerability data.

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