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TI-2026-54110 Aliases CVE-2026-77640GHSA-5g6h-2vr8-m7f4

tor before 0.4.9.9 was prone to an infinite loop when decompressing a truncated zlib/gzip…

Priority LOW 24CWE-1284Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
None
Attack complexity
Low
Impact type
—
Confidentiality · integrity · availability
None · None · Low
Fix status
Fixed

Attack profile from CVSS 3.1 · NVD. Fix status from CNA.

Summary

tor before 0.4.9.9 was prone to an infinite loop when decompressing a truncated zlib/gzip stream with done=1. A truncated stream never reaches Z_STREAM_END, causing zlib to return Z_BUF_ERROR with no input remaining, which buf_add_compress() mistook for a full output buffer and retried forever. Fixed by returning TOR_COMPRESS_ERROR in that case so the caller can abort cleanly. This is TROVE-2026-021.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00378 31st percentileScored 2026-11-07
Fix Fixed Tor (torproject): 0.4.9.9

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
None
Automatable
No
Technical impact
Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
torprojectTor0.2.6.1-alpha to before 0.4.9.90.4.9.9Patch availableCNA
  • Tor Vendortorproject Affected 0.2.6.1-alpha to before 0.4.9.9 Fixed in 0.4.9.9 Patch available CNA

CPE configurations NVD · 1

CPEVersionsRoleVendor
cpe:2.3:a:torproject:tor:*:*:*:*:*:*:*:*before 0.4.9.9Vulnerabletorproject
  • cpe:2.3:a:torproject:tor:*:*:*:*:*:*:*:* Versions before 0.4.9.9 Vulnerable ·torproject

Remediation

  • Fix · CNA Tor (torproject) Fixed in 0.4.9.9

Fixed in the same release

Records fixed by the same vendor advisory or release, as the CNA lists them.

  • Release ·

    torproject Tor 0.4.9.9

    4 records Highest priority Priority MEDIUM 1 MEDIUM, 3 LOW

    Other records, highest priority first

    • TI-2026-54112 Out-of-bounds write in torproject TorPriority MEDIUM 40
    • TI-2026-54111 tor before 0.4.9.9 was prone to a NULL write after free when sending a CONFLUX_SWITCH…Priority LOW 36
    • TI-2026-54109 Tor before 0.4.9.9 was prone to a compression bomb bypass where an attacker could…Priority LOW 30
    Show all 4 records →

Vendor assessments

Red Hat

Red Hat's page for this CVE →

Not affected: 1 product
  • Red Hat

Timeline

  1. 2026-10-02 Threatist record created from CVE-2026-77640
  2. 2026-10-03 Alias added: GHSA-5g6h-2vr8-m7f4

References

Advisory 1

  • TI-2016-07433 Use after free in Mozilla Firefox KEVCVSS 3.1HIGH 7.5
  • TI-2023-09419 The SafeSocks option in Tor before 0.4.7.13 has a logic error in which the unsafe SOCKS4… CVSS 3.1MEDIUM 6.5
  • TI-2018-00448 Use after free in Tor CVSS 3.0HIGH 7.5
  • TI-2026-54108 Race condition in torproject Tor CVSS 3.1CRITICAL 9.0
  • TI-2026-54112 Out-of-bounds write in torproject Tor CVSS 3.1CRITICAL 9.3
  • TI-2026-32508 Tor before 0.4.9.7 has an out-of-bounds read when an END, a TRUNCATE, or a TRUNCATED cell… CVSS 3.1CRITICAL 9.1
See all 47 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences