Certificate authority eMudhra has revoked eight additional intermediate CA certificates after its investigation into a security incident found that a custom Python script containing a bug weakened keys and mishandled others during a key-generation ceremony in April 2025, bringing the total number of affected certificates to 16.
In an incident report published Tuesday, eMudhra said that a custom Python script used to transfer private keys between hardware security modules (HSMs) at its facilities in April 2025 contained a bug that reduced eight ECDSA private keys to a single byte, making them extremely easy to recover. The same script also processed eight RSA private keys that handled sensitive key information in the memory of the computer running the script rather than keeping it protected within the HSM.
While the RSA keys were not weakened like the original eight certificates, eMudhra said it could not demonstrate that it handled them under its certificate security policies. "A re‑import performed from host process memory is not consistent with the CPS §6.2.6 and the RSA objects are therefore treated as not meeting that requirement," the incident report stated. The company revoked the additional eight RSA intermediate CA certificates on November 7, including certificates used to issue TLS and code-signing certificates. Some of the affected RSA intermediates had been actively issuing certificates since May 2026, with the last certificate issued on November 3. eMudhra says the affected customer certificates have also been replaced or migrated.
The incident was first disclosed on October 17, when a security researcher named Wayne discovered that eight eMudhra intermediate CA private keys could be recovered by testing just 256 possible values. Major browsers and operating systems trusted the compromised certificates, potentially allowing attackers to forge certificates for legitimate websites and intercept encrypted communications. Mozilla, Google, Apple, and other software vendors subsequently released protections to block the compromised certificates. Microsoft also released out-of-band Windows updates on October 26 to remove trust in affected eMudhra certificate trust chains on systems that could not receive automatic certificate trust updates.
The company explained that it needed the custom script because "global supply chain constraints" meant it could not acquire the HSMs it wanted to use when creating a set of certificates for use in the USA. It used HSMs made by Utimaco to generate keys and planned to transfer the keys to a different set of HSMs from Crypto4A. The plan went wrong when the company did not notice the errors in its script and did not test the keys it created.
The investigation also found that an earlier problem in June 2025 could have revealed the flaw more than a year before it was discovered. eMudhra detected certificate revocation lists signed with private keys that did not match the corresponding CA certificates. The company fixed the issue by signing the revocation lists with the matching keys but did not investigate why the problem occurred. The new report confirms this was an early warning sign of the faulty key-generation process that went undetected until October 2026.
Following the incident, eMudhra announced it would exit the publicly trusted TLS certificate business and transition its remaining customers to another provider. The company says it plans to stop issuing certificates under its remaining G1 hierarchy by November 16. eMudhra has also commissioned an independent review by KPMG, with findings expected by December 4, to identify improvements to its certificate management and key-generation procedures. The company says it has not detected any evidence that the compromised keys were used maliciously.
Analysis
Why This Matters
- Trust in the web's certificate infrastructure relies on CAs handling private keys securely; eMudhra's failure shows how a single buggy script can compromise that trust for browsers and users worldwide.
- The incident forced major browser vendors (Mozilla, Google, Apple, Microsoft) to issue emergency updates blocking certificates, disrupting services for sites and users relying on eMudhra-issued TLS certificates.
- eMudhra's exit from the TLS business leaves its remaining customers needing to migrate to other providers, highlighting the fragility of certificate supply chains.
Background
Certificate authorities are trusted entities that issue digital certificates used to secure web traffic (HTTPS) and software code signing. eMudhra, an Indian CA, discovered in October 2026 that eight of its intermediate CA private keys were trivially weak after security researcher Wayne noticed the flaw. The company subsequently found another eight certificates were mishandled. Major browsers block untrusted CAs to prevent attackers from forging certificates and intercepting encrypted communications.
Key Perspectives
- eMudhra (via employee Naveen Kumar ML on Bugzilla): The problem stemmed from a buggy Python script run during a single key-generation ceremony on 30 April 2025, where a defect in import code truncated ECDSA private values to a single byte. The company needed the script because supply chain constraints delayed obtaining the desired HSMs.
- Mozilla, Google, Apple, Microsoft: Released protections and updates to block the compromised certificates from being trusted.
What to Watch
- The KPMG independent review, due December 4, which may reveal further process failures or recommend industry-wide changes.
- Whether any malicious use of the compromised certificates is ever detected, which could affect liability and browser trust decisions.
- How the remaining eMudhra G1 certificate hierarchy is wound down by November 16 and whether migration proceeds smoothly.
Checked
12 claims in this story checked against 1 source: 12 supported.
Show each claim
- SupportedeMudhra revoked eight additional intermediate CA certificates after its investigation linked the incident to a buggy Python script.BleepingComputer: “Certificate authority eMudhra has revoked eight additional intermediate CA certificates after an investigation into its recent certificate security incident found improper handling of private keys during the certificate-generation process.”
- SupportedThe incident affected 16 intermediate CA certificates, with both sets affected by a Python script during the April 2025 process.BleepingComputer: “The new revocations bring the total number of affected intermediate CA certificates to 16, including eight previously compromised certificates whose private keys were so weak that anyone could recover them almost instantly. In a new incident report published Tuesday, eMudhra said that both sets of certificates were affected by a custom Python script used to transfer private keys between hardware security modules (HSMs) in April 2025.”
- SupportedThe report states: “A re‑import performed from host process memory is not consistent with the CPS §6.2.6 and the RSA objects are therefore treated as not meeting that requirement,”BleepingComputer: “"A re‑import performed from host process memory is not consistent with the CPS §6.2.6 and the RSA objects are therefore treated as not meeting that requirement," reads the incident report.”
- SupportedThe script reduced eight ECDSA private keys to a single byte, making them extremely easy to recover.BleepingComputer: “However, the script contained a bug that reduced eight ECDSA private keys to a single byte, making them extremely easy to recover.”
- SupportedThe script processed eight RSA private keys in the computer’s memory rather than keeping them protected within the HSM.BleepingComputer: “The same script also processed eight RSA private keys, which handled sensitive key information in the memory of the computer running the script rather than keeping it protected within the HSM.”
- SupportedeMudhra revoked the additional eight RSA intermediate CA certificates on November 7, including certificates used to issue TLS and code-signing certificates.BleepingComputer: “Due to this, the company revoked the additional eight RSA intermediate CA certificates on November 7, including certificates used to issue TLS and code-signing certificates.”
- SupportedSome affected RSA intermediates had issued certificates since May 2026, with the last certificate issued on November 3.BleepingComputer: “Some of the affected RSA intermediates had been actively issuing certificates since May 2026, with the last certificate issued on November 3.”
- SupportedA problem in June 2025 could have revealed the flaw more than a year before it was discovered.BleepingComputer: “The investigation also found that an earlier problem in June 2025 could have revealed the flaw more than a year before it was discovered by a security researcher known as "Wayne."”
- SupportedThe incident was first disclosed on October 17, when researcher Wayne found the private keys could be recovered by testing 256 possible values.BleepingComputer: “the incident was first disclosed on October 17, when a security researcher named Wayne discovered that eight eMudhra intermediate CA private keys could be recovered by testing just 256 possible values.”
- SupportedMozilla, Google, Apple and other software vendors released protections to block the compromised certificates.BleepingComputer: “Mozilla, Google, Apple, and other software vendors subsequently released protections to block the compromised certificates.”
- SupportedMicrosoft released out-of-band Windows updates on October 26 to remove trust in affected eMudhra certificate trust chains on systems that could not receive automatic trust updates.BleepingComputer: “Microsoft also released out-of-band Windows updates on October 26 to remove trust in affected eMudhra certificate trust chains on systems that could not receive automatic certificate trust updates.”
- SupportedeMudhra announced it would exit the publicly trusted TLS certificate business and transition its remaining customers to another provider.BleepingComputer: “Following the incident, eMudhra announced that it would exit the publicly trusted TLS certificate business and transition its remaining customers to another provider.”
