Out-of-bounds write via digest-type parsing
Published Aug 20, 2026 · Updated Aug 20, 2026
Out-of-bounds write in Tor before 0.4.9.9 allows remote attackers to corrupt memory via a crafted consensus or detached signature. The consensus and detached-signature parser mishandles an unexpected signature digest type and writes past the intended buffer during parsing. Exposure depends on processing attacker-controlled or maliciously relayed directory documents; the Tor Project says impact is minor for most roles but potentially major for directory authorities.
Summary
What happened
Out-of-bounds write in Tor before 0.4.9.9 allows remote attackers to corrupt memory via a crafted consensus or detached signature. The consensus and detached-signature parser mishandles an unexpected signature digest type and writes past the intended buffer during parsing. Exposure depends on processing attacker-controlled or maliciously relayed directory documents; the Tor Project says impact is minor for most roles but potentially major for directory authorities.
The record
- CVE
- CVE-2026-77642
- Published
- Aug 20, 2026
- Updated
- Aug 20, 2026
- Vendor
- The Tor Project
- Product
- Tor
- Classifications
- CWE-787, T1499
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Aug 20, 2026CVE publishedPublication date reported by the CVE source.
- Aug 20, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=0.2.8.2-alpha <0.4.9.9
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Public exploit references
No public exploit references are available in this record.
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Technologies
Your stack
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Your stack
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