CVE-2026-77641

tor before 0.4.9.9 was prone to a NULL write after free when sending a CONFLUX_SWITCH cell fails. The return value of relay_send_command_from_edge() was ignored, so a send failure (which calls circuit_mark_for_close() and removes the leg via cfx_del_leg()) would go undetected, causing the caller to write to the now-freed current leg and resulting in a crash. This is TROVE-2026-017.

CVSS v3 6.5 MEDIUM

6.5^/10

CVSS v3 : MEDIUM

Vector :

Exploitability : 2.2 / Impact : 4.2

Attack Vector NETWORK

Attack Complexity HIGH

Privileges Required NONE

User Interaction NONE

Confidentiality Impact NONE

Integrity Impact LOW

Availability Impact HIGH

Scope UNCHANGED

References

Link	Resource
https://gitlab.torproject.org/tpo/core/tor/-/raw/tor-0.4.9.9/ChangeLog	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 antes de la versión 0.4.9.9 era propenso a una escritura NULL tras liberación de memoria cuando falla el envío de una celda CONFLUX_SWITCH. El valor de retorno de relay_send_command_from_edge() fue ignorado, por lo que un fallo de envío (que llama a circuit_mark_for_close() y elimina el tramo a través de cfx_del_leg()) pasaría desapercibido, haciendo que el llamador escribiera en el tramo actual ahora liberado y resultando en un bloqueo. Esto es TROVE-2026-017.

Information

Published : 2026-08-20 21:17

Updated : 2026-10-18 20:10

NVD link : CVE-2026-77641

Mitre link : CVE-2026-77641

CVE.ORG link : CVE-2026-77641

JSON object : View

Products Affected

torproject

tor

CWE

CWE-252

Unchecked Return Value

{"id": "CVE-2026-77641", "cveTags": [], "metrics": {"ssvcV203": [{"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "ssvcData": {"id": "CVE-2026-77641", "role": "CISA Coordinator", "options": [{"exploitation": "none"}, {"automatable": "no"}, {"technicalImpact": "partial"}], "version": "2.0.3", "timestamp": "2026-08-27T15:47:55.296047Z"}}], "cvssMetricV31": [{"type": "Secondary", "source": "cve@mitre.org", "cvssData": {"scope": "UNCHANGED", "version": "3.1", "baseScore": 6.5, "attackVector": "NETWORK", "baseSeverity": "MEDIUM", "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:H", "integrityImpact": "LOW", "userInteraction": "NONE", "attackComplexity": "HIGH", "availabilityImpact": "HIGH", "privilegesRequired": "NONE", "confidentialityImpact": "NONE"}, "impactScore": 4.2, "exploitabilityScore": 2.2}, {"type": "Primary", "source": "nvd@nist.gov", "cvssData": {"scope": "UNCHANGED", "version": "3.1", "baseScore": 8.2, "attackVector": "NETWORK", "baseSeverity": "HIGH", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H", "integrityImpact": "LOW", "userInteraction": "NONE", "attackComplexity": "LOW", "availabilityImpact": "HIGH", "privilegesRequired": "NONE", "confidentialityImpact": "NONE"}, "impactScore": 4.2, "exploitabilityScore": 3.9}]}, "affected": [{"source": "cve@mitre.org", "affectedData": [{"vendor": "torproject", "product": "Tor", "versions": [{"status": "affected", "version": "0.4.8.1-alpha", "lessThan": "0.4.9.9", "versionType": "custom"}], "defaultStatus": "unaffected"}]}], "published": "2026-08-20T21:17:11.517", "references": [{"url": "https://gitlab.torproject.org/tpo/core/tor/-/raw/tor-0.4.9.9/ChangeLog", "tags": ["Release Notes", "Vendor Advisory"], "source": "cve@mitre.org"}], "vulnStatus": "Analyzed", "weaknesses": [{"type": "Secondary", "source": "cve@mitre.org", "description": [{"lang": "en", "value": "CWE-252"}]}], "descriptions": [{"lang": "en", "value": "tor before 0.4.9.9 was prone to a\u00a0NULL write after free when sending a CONFLUX_SWITCH cell fails. The return value of relay_send_command_from_edge() was ignored, so a send failure (which calls circuit_mark_for_close() and removes the leg via cfx_del_leg()) would go undetected, causing the caller to write to the now-freed current leg and resulting in a crash. This is TROVE-2026-017."}, {"lang": "es", "value": "tor antes de la versi\u00f3n 0.4.9.9 era propenso a una escritura NULL tras liberaci\u00f3n de memoria cuando falla el env\u00edo de una celda CONFLUX_SWITCH. El valor de retorno de relay_send_command_from_edge() fue ignorado, por lo que un fallo de env\u00edo (que llama a circuit_mark_for_close() y elimina el tramo a trav\u00e9s de cfx_del_leg()) pasar\u00eda desapercibido, haciendo que el llamador escribiera en el tramo actual ahora liberado y resultando en un bloqueo. Esto es TROVE-2026-017."}], "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"}