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CVE-2026-77639

Quick assessment

Affected
torproject Tor
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

torproject Tor是torproject组织开源的一款匿名通信软件。 torproject Tor 0.4.9.9之前版本存在授权问题漏洞，该漏洞源于压缩炸弹绕过，攻击者可串联多个gzip或zlib子流，每个子流略低于检测阈值，从而完全绕过压缩炸弹检查，可能导致拒绝服务攻击。

CVSS 5.3 · Medium EPSS 0.39% · P31

Possible ATT&CK Techniques 1 AI

T1496 · Resource Hijacking

Affected Version Matrix 1

VendorProduct Version RangeStatus
torproject Tor 0.3.1.1-alpha< 0.4.9.9 affected
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I. Basic Information for CVE-2026-77639

Vulnerability Information
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Vulnerability Title
N/A
Source: CVE Program / CVE List V5
Vulnerability Description
Tor before 0.4.9.9 was prone to a compression bomb bypass where an attacker could concatenate many gzip or zlib sub-streams, each just under the per-stream detection threshold, to avoid the compression bomb check entirely. This is TROVE-2026-022.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
Source: CVE Program / CVE List V5
Vulnerability Type
未保护的候选通道
Source: CVE Program / CVE List V5
Vulnerability Title
torproject Tor 授权问题漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
torproject Tor是torproject组织开源的一款匿名通信软件。 torproject Tor 0.4.9.9之前版本存在授权问题漏洞，该漏洞源于压缩炸弹绕过，攻击者可串联多个gzip或zlib子流，每个子流略低于检测阈值，从而完全绕过压缩炸弹检查，可能导致拒绝服务攻击。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
torproject Tor 0.3.1.1-alpha ~ 0.4.9.9 -

II. Public POCs for CVE-2026-77639

# POC Description Source Link Shenlong Link
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III. Intelligence Information for CVE-2026-77639

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Other References for CVE-2026-77639 (1)

Same Patch Batch · torproject · 2026-08-20 · 7 CVEs total

CVE-2026-77638 8.9 HIGH torproject Tor 竞争条件问题漏洞
CVE-2026-77642 7.5 HIGH torproject Tor 缓冲区错误漏洞
CVE-2026-77584 7.0 HIGH torproject Tor 竞争条件问题漏洞
CVE-2026-77641 6.5 MEDIUM torproject Tor 异常处理不当漏洞
CVE-2026-77587 5.9 MEDIUM torproject Tor 资源管理错误漏洞
CVE-2026-77640 3.7 LOW torproject Tor 输入验证错误漏洞

IV. Related Vulnerabilities

Same product: Tor
Same vendor: torproject
Same weakness: CWE-420

V. Comments for CVE-2026-77639

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