CVE-2026-77640

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.

CVSS v3 3.7 LOW

3.7^/10

CVSS v3 : LOW

Vector :

Exploitability : 2.2 / Impact : 1.4

Attack Vector NETWORK

Attack Complexity HIGH

Privileges Required NONE

User Interaction NONE

Confidentiality Impact NONE

Integrity Impact NONE

Availability Impact LOW

Scope UNCHANGED

References

Link	Resource
https://gitlab.torproject.org/tpo/core/tor/-/raw/tor-0.4.9.9/ChangeLog	Permissions Required Release Notes Vendor Advisory

Configurations

Configuration 1 (hide)

cpe:2.3:a:torproject:tor:*:*:*:*:*:*:*:*

History

18 Oct 2026, 20:10

Type	Values Removed	Values Added
Summary		(es) tor anterior a la versión 0.4.9.9 era propenso a un bucle infinito al descomprimir un flujo zlib/gzip truncado con done=1. Un flujo truncado nunca alcanza Z_STREAM_END, lo que hacía que zlib devolviera Z_BUF_ERROR sin entrada restante, lo que buf_add_compress() confundió con un búfer de salida lleno y reintentó indefinidamente. Solucionado devolviendo TOR_COMPRESS_ERROR en ese caso para que el llamador pueda abortar limpiamente. Esto es TROVE-2026-021.

Information

Published : 2026-08-20 21:17

Updated : 2026-10-18 20:10

NVD link : CVE-2026-77640

Mitre link : CVE-2026-77640

CVE.ORG link : CVE-2026-77640

JSON object : View

Products Affected

torproject

tor

CWE

CWE-1284

Improper Validation of Specified Quantity in Input

{"id": "CVE-2026-77640", "cveTags": [], "metrics": {"ssvcV203": [{"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "ssvcData": {"id": "CVE-2026-77640", "role": "CISA Coordinator", "options": [{"exploitation": "none"}, {"automatable": "no"}, {"technicalImpact": "partial"}], "version": "2.0.3", "timestamp": "2026-08-21T19:51:18.580818Z"}}], "cvssMetricV31": [{"type": "Secondary", "source": "cve@mitre.org", "cvssData": {"scope": "UNCHANGED", "version": "3.1", "baseScore": 3.7, "attackVector": "NETWORK", "baseSeverity": "LOW", "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L", "integrityImpact": "NONE", "userInteraction": "NONE", "attackComplexity": "HIGH", "availabilityImpact": "LOW", "privilegesRequired": "NONE", "confidentialityImpact": "NONE"}, "impactScore": 1.4, "exploitabilityScore": 2.2}, {"type": "Primary", "source": "nvd@nist.gov", "cvssData": {"scope": "UNCHANGED", "version": "3.1", "baseScore": 5.3, "attackVector": "NETWORK", "baseSeverity": "MEDIUM", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L", "integrityImpact": "NONE", "userInteraction": "NONE", "attackComplexity": "LOW", "availabilityImpact": "LOW", "privilegesRequired": "NONE", "confidentialityImpact": "NONE"}, "impactScore": 1.4, "exploitabilityScore": 3.9}]}, "affected": [{"source": "cve@mitre.org", "affectedData": [{"vendor": "torproject", "product": "Tor", "versions": [{"status": "affected", "version": "0.2.6.1-alpha", "lessThan": "0.4.9.9", "versionType": "custom"}], "defaultStatus": "unaffected"}]}], "published": "2026-08-20T21:17:11.373", "references": [{"url": "https://gitlab.torproject.org/tpo/core/tor/-/raw/tor-0.4.9.9/ChangeLog", "tags": ["Permissions Required", "Release Notes", "Vendor Advisory"], "source": "cve@mitre.org"}], "vulnStatus": "Analyzed", "weaknesses": [{"type": "Secondary", "source": "cve@mitre.org", "description": [{"lang": "en", "value": "CWE-1284"}]}], "descriptions": [{"lang": "en", "value": "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."}, {"lang": "es", "value": "tor anterior a la versi\u00f3n 0.4.9.9 era propenso a un bucle infinito al descomprimir un flujo zlib/gzip truncado con done=1. Un flujo truncado nunca alcanza Z_STREAM_END, lo que hac\u00eda que zlib devolviera Z_BUF_ERROR sin entrada restante, lo que buf_add_compress() confundi\u00f3 con un b\u00fafer de salida lleno y reintent\u00f3 indefinidamente. Solucionado devolviendo TOR_COMPRESS_ERROR en ese caso para que el llamador pueda abortar limpiamente. Esto es TROVE-2026-021."}], "lastModified": "2026-10-18T20:10:00.110", "configurations": [{"nodes": [{"negate": false, "cpeMatch": [{"criteria": "cpe:2.3:a:torproject:tor:*:*:*:*:*:*:*:*", "vulnerable": true, "matchCriteriaId": "F8FF755D-D472-48A8-9F10-F64B625DD9C3", "versionEndExcluding": "0.4.9.9"}], "operator": "OR"}]}], "sourceIdentifier": "cve@mitre.org"}