Eight eMudhra CA keys were guessable; Windows drops seven certificates, and Java, Python, Go and GitLab need…
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notable
1 notable
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no sector or region stated
Sources cited
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17 hosts
Action items (3)
Do-now tasks recorded on the entries about Oracle Global Lifecycle Management OPatch, newest first. Check the date before acting on an older one.
Update every non-browser TLS client that keeps its own CA bundle or does not check revocation to a fixed version: standalone Java runtimes, including those already updated on 2026-10-21, to the update of Oracle's Security Alert CVE-2026-114820 or OpenJDK (Oracle Database Server, Autonomous Health Framework and OPatch installations too), Python 3.15.2, 3.14.10, 3.13.18, 3.12.16 or 3.11.18 together with pip 26.2.2 or later, Go 1.27.3 or 1.26.10, and self-managed GitLab to a fixed patch release together with GitLab Runner 19.5.1; then confirm with curl against the incident tracker's test host that the client rejects the certificate.
Replace, by hand where the ACME client does not support ACME Renewal Information, every TLS certificate your organisation holds that chains to emSign ECC Root CA - G3 or to another of the seven certificates Microsoft removed from the Windows and Edge trust lists, because Chrome's removal of the G3 root was due on 2026-10-27 and the Windows change takes effect when the trust-list update reaches a device; deliver the updated Disallowed Certificate Trust List and the trust-list changes Microsoft describes, including its out-of-band update of 2026-10-26, to Windows devices that do not receive automatic certificate-trust updates.
Apply Cisco's remediation now for the products its eMudhra advisory (version 1.5) lists with a fix or a procedure available: the guidance for Secure Firewall ASA, FTD and FMC, Secure Email Gateway and Secure Email and Web Manager (run the updatenow command where updates are manual), Duo Access Gateway 3.2.0, Duo Network Gateway 3.4.1, Duo Agentic Authorization Connector 1.0.1 and ThousandEyes Enterprise Agent (Application-hosting Agent 5.2.2).
1 technique observed across 1 entry about this entity, derived from entry metadata and body evidence, never asserted without a published entry behind it · pinned to MITRE ATT&CK v20.0 · compare on the matrix · Navigator layer (JSON)
Credential AccessAdversary-in-the-Middle
CollectionAdversary-in-the-Middle
Credential Access TA0006
T1557Adversary-in-the-Middle×1
Adversaries may attempt to position themselves between two or more networked devices using an adversary-in-the-middle (AiTM) technique to support follow-on behaviors such as Network Sniffing, Transmitted Data Manipulation, or replay attacks (Exploitation for Credential Access). By abusing features of common networking protocols that can determine the flow of network traffic (e.g. ARP, DNS, LLMNR, etc.), adversaries may force a device to communicate through an adversary controlled system so they can collect information or perform additional actions.
Adversaries may attempt to position themselves between two or more networked devices using an adversary-in-the-middle (AiTM) technique to support follow-on behaviors such as Network Sniffing, Transmitted Data Manipulation, or replay attacks (Exploitation for Credential Access). By abusing features of common networking protocols that can determine the flow of network traffic (e.g. ARP, DNS, LLMNR, etc.), adversaries may force a device to communicate through an adversary controlled system so they can collect information or perform additional actions.
On 2026-10-17 a researcher reported to the Chrome Root Program, and Mozilla received a report the same day, that the private keys of eight eMudhra subordinate CA certificates were compromised: the keys were generated with insufficient randomness, which lets anyone forge trusted HTTPS certificates to impersonate any website against clients that have not removed trust in those CAs (Google, 2026-10-20; Mozilla, 2026-10-20). BleepingComputer, citing Mozilla's incident report, says all eight were P-384 keys generated in April 2025 with values below 256, so testing 256 numbers recovers a key, and that eMudhra blames a key-generation script error and found no evidence of end-user certificates (BleepingComputer, 2026-10-20). Google reports that no certificates chaining to the six TLS intermediates were logged to Certificate Transparency before it blocked them, so CT-enforcing clients such as Chrome could not have been attacked (Google, 2026-10-20); the tracker says it is not known whether attackers used the flaw against other clients (Dennis Jackson, 2026-10-20).
Chrome blocked the intermediates on 2026-10-17, Firefox through OneCRL the same day, Microsoft platforms on 2026-10-20 and Apple devices on 2026-10-22, and eMudhra revoked all eight (Dennis Jackson, 2026-10-20; BleepingComputer, 2026-10-20). Microsoft went further: an out-of-band Windows update of 2026-10-26 removes seven certificates, six eMudhra G3 roots and an AAA Certificate Services cross-sign, from the Windows trust list, and the same seven left the Edge trust list on 2026-10-27 (Microsoft, 2026-10-26). Google removed the root that signed them, emSign ECC Root CA - G3, from the Chrome Root Store, with the removal expected to reach devices on 2026-10-27, after which some legitimate certificates chaining to it will stop working in Chrome (Google, 2026-10-20). Go 1.27.3 and 1.26.10 filter chains that contain the intermediates in crypto/x509, tracked as CVE-2026-111943 (Go team, 2026-10-20), and GitLab's release of 2026-10-29 removes trust for the eight intermediates in self-managed CE and EE, with GitLab Runner 19.5.1 and the AI Gateway needing separate updates (GitLab, 2026-10-29).
Oracle's Security Alert of 2026-10-21 for CVE-2026-91403 (CVSS 3.1 9.1, component JSSE, remotely exploitable without authentication through the component's APIs) provided Java updates that distrust the impacted eMudhra intermediate CA certificates (Oracle, 2026-10-21), and a second Security Alert of 2026-10-24, CVE-2026-114820 (CVSS 3.1 9.1, same component and exposure), provides updates that remove the impacted root CA certificates and, from its revision of 2026-10-30, also covers the Java component of Oracle Database Server (not client-only installations), Autonomous Health Framework and OPatch (Oracle, 2026-10-30). OpenJDK's guidance tells users of a standalone runtime to act immediately even if they updated in the past few days, preferably by installing an update whose release note names JDK-8395690 and CVE-2026-114820 (OpenJDK, 2026-10-24). If no update is available, OpenJDK gives two alternatives: delete the aliases emsignrootcag1, emsignrootcag2, emsigneccrootcag3 and comodoaaaca from the runtime's cacerts keystore and restart it, repeating for each installation, or enable revocation checking with -Dcom.sun.net.ssl.checkRevocation=true and -Dcom.sun.security.enableCRLDP=true on the application's java command line (OpenJDK, 2026-10-24). OpenJDK packages from Red Hat, Oracle Linux, Fedora, Arch Linux and Gentoo most likely use the operating system's certificates; Debian, Devuan and Ubuntu need a manual workaround because updating ca-certificates and ca-certificates-java does not refresh the keystore (as superuser, remove /etc/ssl/certs/java/cacerts and run update-ca-certificates --fresh) (OpenJDK, 2026-10-24).
Triage: a site that still chains to emSign ECC Root CA - G3 failing in Chrome after 2026-10-27, or a certificate that chains to one of the seven certificates Microsoft removed failing in Windows or Edge once the change reaches the device, is the announced root removal, not an attack (Google, 2026-10-20; Microsoft, 2026-10-26).
enabling anyone to forge trusted HTTPS certificates to impersonate any website against clients that have not yet removed trust in those CAs.
This Security Alert addresses CVE-2026-91403 by providing Java updates which distrusts the set of impacted intermediate CA certificates related to eMudhra.
Python has added a denylist for known compromised certificates to the "ssl" module to ensure user safety even without certificate revocation configured.
Chrome has told eMudhra that standard ACME clients do not replace certificates outside their renewal window unless they support ACME Renewal Information (ARI) or someone steps in by hand.
On October 26, Microsoft released an out-of-band Windows update that removes seven certificates associated with the affected hierarchies: six eMudhra G3 roots and an AAA Certificate Services cross-sign, from the Windows trust list.
Microsoft Security Response Center
GitLab has removed trust for eight eMudhra intermediate CA certificates whose private keys have been compromised.
GitLab
The Cisco PSIRT is not aware of any malicious use of the issue that is described in this advisory.
On 2026-10-21 Oracle issued Security Alert CVE-2026-91403 and the OpenJDK project an advisory for the same event, which reaches Java runtimes as well; Oracle says it also applies to sandboxed Java Web Start and applet clients (Oracle, 2026-10-21). Affected are Oracle Java SE 8u511, 8u511-perf, 11.0.33, 17.0.21, 21.0.13, 25.0.5 and 27.0.1, GraalVM for JDK 17.0.21 and 21.0.13 and GraalVM Enterprise Edition 21.3.20, and OpenJDK lists 27.0.1, 25.0.5, 21.0.13, 17.0.21, 11.0.32.1 and 8u504 and earlier (Oracle, 2026-10-21; OpenJDK, 2026-10-21). Compare the full build string, not the release number, against Oracle's affected list. NCSC.ch's advisory of 2026-10-22 lists the exploitation status as unknown and the OpenJDK guidance as the temporary mitigation (NCSC.ch, 2026-10-22).
Oracle's second Security Alert of 2026-10-24, CVE-2026-114820 (CVSS 3.1 9.1, component JSSE, remotely exploitable without authentication through the component's APIs), provides Java updates that remove the impacted root CA certificates related to eMudhra (Oracle, 2026-10-24). Its affected list names Oracle Java SE 8u511-b32, 11.0.33.0.2, 17.0.21.0.2, 21.0.13.0.2, 25.0.5.0.2 and 27.0.1.0.2, and the OpenJDK advisory of the same day lists 27.0.1.0.2, 25.0.5.0.2, 21.0.13.0.2, 17.0.21.0.2, 11.0.32.1 and 8u504 and earlier as affected (Oracle, 2026-10-24; OpenJDK, 2026-10-24). OpenJDK tells users of a standalone runtime to act immediately even if they updated in the past few days, by installing an update whose release note names JDK-8395690 and CVE-2026-114820 or, failing that, by deleting the cacerts aliases emsignrootcag1, emsignrootcag2, emsigneccrootcag3 and comodoaaaca or enabling revocation checking (OpenJDK, 2026-10-24). The same page now says Debian, Devuan and Ubuntu OpenJDK packages need the keystore recreated by hand, because updating ca-certificates and ca-certificates-java does not refresh it, which replaces the earlier statement that updating the operating system's certificates suffices there (OpenJDK, 2026-10-24).
The Python Software Foundation announced CVE-2026-115557 on 2026-10-24: the ssl module now carries a denylist of known compromised certificates that is rejected whatever the SSLContext policy, so it works without revocation checking (Python Software Foundation, 2026-10-24). ENISA's record scores it 9.4 (CVSS 4.0) and lists CPython before 3.16.0 as affected, and the announcement names no release that carries the denylist (ENISA EUVD, 2026-10-24). The incident tracker lists Python 3.15.1, 3.14.9 and 3.13.17 and pip 26.2.2 as patched, and Christian Heimes stresses in the announcement thread that pip before 26.2.2 keeps trusting the compromised intermediates whatever the system trust store holds, because it always loads its own vendored certifi (Dennis Jackson, 2026-10-20; Python Discourse, 2026-10-20).
Cisco's informational advisory, version 1.1 of 2026-10-24, lists as impacted with remediation a TLS policy that blocks the known eMudhra issuers on Secure Firewall Management Center, Duo Access Gateway 3.2.0, Duo Network Gateway 3.4.1, Duo Agentic Authorization Connector 1.0.1, ThousandEyes Enterprise Agent (Application-hosting Agent 5.2.2, 2026-10-23), Meraki MV Smart Camera Firmware (2026-11-18), IOS XR 26.4.1 (2026-11-30) and Ultra Cloud Core Subscriber Microservices Infrastructure 2026.04.1 (November 2026), keeps further products under investigation, and says Cisco PSIRT is not aware of malicious use (Cisco PSIRT, 2026-10-24).
eMudhra's board decided on 2026-10-22 to leave the global SSL/TLS certificate business, and its G1 RSA roots keep serving customers during the transition (eMudhra, 2026-10-22). The Hacker News relays Chrome's count of about 30,800 unexpired certificates under the emSign ECC Root CA - G3, which Chrome stops trusting on 2026-10-27, as of 2026-10-21, 99.9 percent of them issued through InCommon, and relays Chrome's point that standard ACME clients do not replace a certificate outside its renewal window unless they support ACME Renewal Information or someone steps in by hand (The Hacker News, 2026-10-22).
Microsoft released an out-of-band Windows update on 2026-10-26 that removes seven certificates associated with the affected hierarchies, six eMudhra G3 roots and an AAA Certificate Services cross-sign, from the Windows trust list, and removed the same seven from the Edge trust list on 2026-10-27; removing a root is a separate and broader decision than blocking the compromised intermediates, which Microsoft had done through its Disallowed Certificate Trust List on 2026-10-20 (Microsoft, 2026-10-26). Microsoft tells organizations to keep automatic trust-list updates flowing, to make sure disconnected Windows devices receive the updated trust lists, and to replace certificates that chain to one of the seven before the change reaches their devices, and it warns that software that does not check revocation or the disallowed list could still accept certificates tied to the compromised keys if trust is restored locally (Microsoft, 2026-10-26).
Cisco's advisory is at version 1.5 of 2026-10-30. It lists remediation for Secure Firewall ASA, FTD and FMC (guidance page), Secure Email Gateway and Secure Email and Web Manager (updated automatically to Trusted Root 2.8, with the updatenow command where updates are manual) and Packaged and Unified Contact Center Enterprise (CSCwx36769); it dates the fixes for ISE and ISE-PIC to ISE 3.5P5 in December 2026 and 3.3P13 and 3.4P8 in April 2027, and still lists IOS XE Software, MDS 9000 and Nexus switches among the impacted products under investigation; Cisco says it is not aware of malicious use (Cisco PSIRT, 2026-10-30). GitLab's patch release of 2026-10-29 removes trust for the eight intermediates in self-managed CE and EE and says GitLab Runner 19.5.1 and the AI Gateway must be updated separately because they verify certificates on their own (GitLab, 2026-10-29). Python's expedited releases of 2026-10-26, 3.15.2, 3.14.10, 3.13.18, 3.12.16 and 3.11.18, now carry the built-in denylist for the compromised intermediates (Python Insider, 2026-10-26). Oracle's revision 2 of Security Alert CVE-2026-114820, dated 2026-10-30, adds the Java component of Oracle Database Server (19.3 to 19.32, 21.3 to 21.23 and 23.4.0 to 23.26.3, not client-only installations), Autonomous Health Framework Trace File Analyzer 26.3 to 26.10, OPatch 12.2.0.1.16 to 12.2.0.1.52 and Hospitality Cruise Shipboard Property Management 23.3.4 to 23.3.6, each remotely exploitable without authentication at CVSS 3.1 9.1 (Oracle, 2026-10-30).