{"id":"CVE-2026-11835","state":"PUBLISHED","title":"Caliptra Update-Reset Secure-Boot Bypass via Attacker-Chosen AXI Staging Address (TOCTOU)","description":"Time-of-check time-of-use (TOCTOU) vulnerability combined with missing input validation in Caliptra Core ROM (UpdateResetFlow::run()) in subsystem mode allows a compromised local attacker to silently bypass secure boot by supplying an AXI staging address that is not validated against the strap-configured SS_EXTERNAL_STAGING_AREA_BASE_ADDR, enabling firmware to be modified between verification and loading into ICCM. Attestation continues to report the originally verified image digest, masking the compromise. Exploitation requires a compromised MCU firmware with AXI manager access to unprotected SRAM reachable by Caliptra.\n\nThis issue affects Core ROM: 2.1.0 through 2.1.1.","publishedAt":"2026-08-04T00:03:23.278Z","updatedAt":"2026-08-04T21:25:26.656Z","severity":{"score":5.6,"label":"Medium","version":"4.0","vector":"CVSS:4.0/AV:L/AC:H/AT:P/PR:H/UI:N/VC:L/VI:H/VA:N/SC:N/SI:N/SA:N","source":"Caliptra"},"assigner":"Caliptra","products":["Caliptra Core ROM"],"affected":[{"vendor":"Caliptra","product":"Core ROM","packageName":"Core ROM","defaultStatus":"unaffected","versions":[{"version":"2.1.0","status":"affected","lessThanOrEqual":"2.1.1","versionType":"semver"},{"version":"2.1.2","status":"unaffected","versionType":"semver"}],"collectionURL":"https://github.com/chipsalliance/caliptra-sw","modules":["UpdateResetFlow::run()"]}],"references":["https://github.com/chipsalliance/caliptra-sw/security/advisories/GHSA-49mm-5gq5-v97f"],"weaknesses":["CWE-367","CWE-20"],"ingestedAt":"2026-10-29T20:10:52.580Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/11xxx/CVE-2026-11835.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-11835","state":"PUBLISHED","datePublished":"2026-08-04T00:03:23.278Z","dateUpdated":"2026-08-04T21:25:26.656Z","assignerShortName":"Caliptra","assignerOrgId":"b01ddd03-5ef6-483b-b2c5-acba77f1a554","dateReserved":"2026-06-09T23:30:36.611Z"},"containers":{"cna":{"title":"Caliptra Update-Reset Secure-Boot Bypass via Attacker-Chosen AXI Staging Address (TOCTOU)","descriptions":[{"lang":"en","value":"Time-of-check time-of-use (TOCTOU) vulnerability combined with missing input validation in Caliptra Core ROM (UpdateResetFlow::run()) in subsystem mode allows a compromised local attacker to silently bypass secure boot by supplying an AXI staging address that is not validated against the strap-configured SS_EXTERNAL_STAGING_AREA_BASE_ADDR, enabling firmware to be modified between verification and loading into ICCM. Attestation continues to report the originally verified image digest, masking the compromise. Exploitation requires a compromised MCU firmware with AXI manager access to unprotected SRAM reachable by Caliptra.\n\nThis issue affects Core ROM: 2.1.0 through 2.1.1."}],"affected":[{"vendor":"Caliptra","product":"Core ROM","packageName":"Core ROM","defaultStatus":"unaffected","versions":[{"version":"2.1.0","status":"affected","lessThanOrEqual":"2.1.1","versionType":"semver"},{"version":"2.1.2","status":"unaffected","versionType":"semver"}],"collectionURL":"https://github.com/chipsalliance/caliptra-sw","modules":["UpdateResetFlow::run()"]}],"references":[{"url":"https://github.com/chipsalliance/caliptra-sw/security/advisories/GHSA-49mm-5gq5-v97f"}],"metrics":[{"format":"CVSS","scenarios":[{"lang":"en","value":"GENERAL"}],"cvssV4_0":{"attackVector":"LOCAL","attackComplexity":"HIGH","attackRequirements":"PRESENT","privilegesRequired":"HIGH","userInteraction":"NONE","vulnConfidentialityImpact":"LOW","subConfidentialityImpact":"NONE","vulnIntegrityImpact":"HIGH","subIntegrityImpact":"NONE","vulnAvailabilityImpact":"NONE","subAvailabilityImpact":"NONE","exploitMaturity":"NOT_DEFINED","Safety":"NOT_DEFINED","Automatable":"NOT_DEFINED","Recovery":"NOT_DEFINED","valueDensity":"NOT_DEFINED","vulnerabilityResponseEffort":"NOT_DEFINED","providerUrgency":"NOT_DEFINED","version":"4.0","baseSeverity":"MEDIUM","baseScore":5.6,"vectorString":"CVSS:4.0/AV:L/AC:H/AT:P/PR:H/UI:N/VC:L/VI:H/VA:N/SC:N/SI:N/SA:N"}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-367","lang":"en","description":"CWE-367 Time-of-check Time-of-use (TOCTOU) Race Condition","type":"CWE"}]},{"descriptions":[{"cweId":"CWE-20","lang":"en","description":"CWE-20 Improper Input Validation","type":"CWE"}]}],"providerMetadata":{"shortName":"Caliptra","orgId":"b01ddd03-5ef6-483b-b2c5-acba77f1a554","dateUpdated":"2026-08-04T21:25:26.656Z"},"datePublic":"2026-08-03T00:00:00.000Z","impacts":[{"capecId":"CAPEC-29","descriptions":[{"lang":"en","value":"CAPEC-29 Leveraging Time-of-Check and Time-of-Use (TOCTOU) Race Conditions"}]}],"tags":["x_open-source"],"credits":[{"lang":"en","value":"Alex Matrosov with Claude, Anthropic","type":"finder"}],"source":{"discovery":"INTERNAL"},"x_generator":{"engine":"Vulnogram 1.0.2"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2026-08-04T19:21:52.034967Z","id":"CVE-2026-11835","options":[{"Exploitation":"none"},{"Automatable":"no"},{"Technical Impact":"partial"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-08-04T19:24:22.359Z"}}]}}}