[NEW] [high] Tor: Multiple vulnerabilities

highCVE-2026-77639 CVE-2026-77640 CVE-2026-77641 CVE-2026-77642 CVE-2026-77584 CVE-2026-77587

A remote anonymous attacker can exploit multiple vulnerabilities in Tor to bypass security measures, manipulate data, disclose information, or trigger a denial-of-service condition.

CSIRTS triage

vendor: Tor product: Tor Authentication bypass Information disclosure Denial of serviceOther

What: Multiple vulnerabilities in Tor enable authentication bypass, data manipulation, information disclosure, and denial of service.
Who is affected: Tor relay and client deployments.
Urgency: High: severity rated high; authentication bypass in Tor impacts network security.
Action: Apply Tor security updates; check torproject.org for patched versions and release notes.

AI-assisted analysis generated from the source advisory — verify against the original.

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Details

Source: CERT-Bund (BSI) Security Advisories (DE · national-cert · site)
Severity: high
Published: 2026-08-21
Exploitation: Not in CISA KEV at last sync
Language: Machine-translated to English — verify against the original

Original advisory: https://wid.cert-bund.de/portal/wid/securityadvisory?name=WID-SEC-2026-2959

Exploitation outlook

EPSS (FIRST.org) estimates each CVE’s probability of exploitation in the next 30 days — here is the CSIRTS.com read on those numbers.

Low exploitation riskCVE-2026-776390.25% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 16% of all EPSS-scored CVEs.
Low exploitation riskCVE-2026-776400.21% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 12% of all EPSS-scored CVEs.
Low exploitation riskCVE-2026-776410.19% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 9% of all EPSS-scored CVEs.
Low exploitation riskCVE-2026-776420.19% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 9% of all EPSS-scored CVEs.
Low exploitation riskCVE-2026-775840.18% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 7% of all EPSS-scored CVEs.
Low exploitation riskCVE-2026-775870.22% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 13% of all EPSS-scored CVEs.
Low exploitation riskCVE-2026-776380.17% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 7% of all EPSS-scored CVEs.

Referenced CVEs

CVE	CSIRTS overview	External
CVE-2026-77639	coverage & exploitation status	NVD · CVE.org
CVE-2026-77640	coverage & exploitation status	NVD · CVE.org
CVE-2026-77641	coverage & exploitation status	NVD · CVE.org
CVE-2026-77642	coverage & exploitation status	NVD · CVE.org
CVE-2026-77584	coverage & exploitation status	NVD · CVE.org
CVE-2026-77587	coverage & exploitation status	NVD · CVE.org
CVE-2026-77638	coverage & exploitation status	NVD · CVE.org

Same CVEs, other sources

How other CERTs, PSIRTs and databases cover the vulnerabilities in this advisory.

Recent advisories for Tor

A cluster of recent advisories against the same product widens the attack surface — attackers routinely chain freshly published CVEs on one product, so review these together.

highCVE-2026-77642: tor before 0.4.9.9 was prone to an out-of-bounds write when parsing a consensus or detached si…nvd · 2026-08-20
mediumCVE-2026-77641: tor before 0.4.9.9 was prone to a NULL write after free when sending a CONFLUX_SWITCH cell fai…nvd · 2026-08-20
lowCVE-2026-77640: tor before 0.4.9.9 was prone to an infinite loop when decompressing a truncated zlib/gzip stre…nvd · 2026-08-20
mediumCVE-2026-77639: Tor before 0.4.9.9 was prone to a compression bomb bypass where an attacker could concatenate …nvd · 2026-08-20
highCVE-2026-77638: Tor before 0.4.9.11 is prone to a race condition where in just the right circumstances a rende…nvd · 2026-08-20
mediumCVE-2026-77587: Tor before 0.4.9.11 is prone to a use-after-free (and potential double free) of a conflux obje…nvd · 2026-08-20