Mozilla::CA: Trust in compromised eMudhra intermediate CA certificates
Summary
The Perl module Mozilla::CA ships a CA certificate bundle that contains the root emSign ECC Root CA - G3. This root chains to eight eMudhra intermediate CAs whose private keys are publicly recoverable. An attacker who can intercept or redirect client traffic can use these keys to impersonate a TLS server, if the client uses this bundle for certificate validation.
Affected
- Mozilla-CA (Perl distribution) versions before 20261020
- Perl clients such as LWP and HTTP::Tiny only when they use the Mozilla::CA bundle as CA store
- Other distributions and Windows or macOS Perl installs: Unknown.
Fixed in
- Mozilla-CA 20261020 or later
- RHEL: not affected, because the packaged perl-Mozilla-CA uses the system store
- Rocky Linux: fixed OS CA bundle builds dated 22 to 26 October 2026
- Debian: Unknown.
Workaround
- If you cannot patch yet, remove the affected roots from the bundle after testing
- Removing emSign ECC Root CA - G3 alone is not enough, because Sectigo cross-signs chain to AAA Certificate Services
- Trust stores that are not updated automatically must block the compromised intermediates manually
Exploitation
- No confirmed in-the-wild exploitation known as of 31 October 2026
- Several researchers independently recovered the private keys, and some disclosed this publicly
- No public proof of concept specific to Mozilla::CA found.
Our recommendation
- Check whether any application uses Perl Mozilla::CA or the bundle it ships
- Update Mozilla-CA to 20261020 or later, or install the operating system vendor's CA updates if the system store is used
- Check the CA store used by each client, including configuration and environment variables
- Review proxies and non-browser clients, as they often do not enforce Certificate Transparency
- Monitor for certificate errors and unexpected certificate changes
Public exploits
PoC-in-GitHub, Metasploit and Exploit-DB list nothing for this CVE.
Research sources
- Bugzilla: eMudhra private key compromise of intermediate certificates bugzilla.mozilla.org
- eMudhra Intermediate CA Compromise emudhra.we-have-a-problem.com
- Mozilla-CA 20261020 changes metacpan.org
- oss-security advisory www.openwall.com
- Red Hat CVE record access.redhat.com
- Rocky Linux security advisory kb.ciq.com
- Vulners NVD record vulners.com
Researched and written up in English and German by an AI (Claude by Anthropic) based on NVD, CISA, EPSS and the sources listed. The vendor information is authoritative. Researched on 31 Oct 2026, 05:46.
Original description (NVD)
Mozilla::CA versions before 20261020 for Perl provide a CA certificate bundle containing a root linked to compromised intermediates. The bundle includes "emSign ECC Root CA - G3", which provides a trust path for intermediate certificates whose private keys are publicly available. An attacker able to intercept or redirect client traffic may use these keys to impersonate a TLS server. LWP, HTTP::Tiny and other clients normally use IO::Socket::SSL, which looks for CA certificates in OpenSSL's default locations before falling back to Mozilla::CA. Configuration and environment variables can override this selection. Users should check which CA store their client uses. If it uses the system store, check for and install the operating system vendor's updates for this incident.
Sources
The tracker combines official, freely usable data sources – updated continuously:
- NVD (NIST) – CVEs, rating (CVSS), affected products
- CISA KEV – vulnerabilities confirmed by CISA as actively exploited
- CISA Vulnrichment – CISA assessment (SSVC) in the official CVE record
- FIRST EPSS – probability of exploitation
- Microsoft MSRC – Patch Tuesday: vulnerabilities, severity, updates
- PoC-in-GitHub – public proof-of-concept repositories
- Metasploit (Rapid7) – modules of the Metasploit Framework
- Exploit-DB (OffSec) – archive of public exploits (links only)
- Patch days: official vendor pages (linked per vendor) (Vendor patch days)
This product uses data from the NVD API but is not endorsed or certified by the NVD. EPSS data © FIRST.org.
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