CVE-2026-87737: 
Linux Debian vulnerability analysis and mitigation

CVE-2026-87737 is a timing side-channel vulnerability in the mirage-crypto-ec package for OCaml, affecting all versions before 2.4.0. The flaw exists in NIST elliptic-curve scalar multiplication, where the time required for a lookup operation can depend on a secret value, potentially leaking cryptographic key material through timing analysis. It was published on September 9, 2026, and carries a CVSS v3.1 base score of 5.9 (Medium) (GitHub Advisory).

The vulnerability is classified as CWE-208 (Observable Timing Discrepancy), mapped to CAPEC-462 (Cross-Domain Search Timing). During NIST elliptic-curve scalar multiplication in mirage-crypto-ec, a table lookup operation takes a variable amount of time depending on a secret scalar value. An attacker capable of making repeated cryptographic requests and measuring response times can statistically recover the secret key through timing analysis. Exploitation requires high attack complexity, as it involves collecting and analyzing many timing measurements over a network connection (GitHub Advisory).

Successful exploitation allows an unauthenticated remote attacker to extract secret cryptographic key material from applications using the vulnerable mirage-crypto-ec library. The impact is limited to confidentiality — integrity and availability are not affected. Compromised private keys could enable impersonation, decryption of protected communications, or forging of digital signatures in systems relying on NIST elliptic-curve cryptography (GitHub Advisory).

There is no known public proof-of-concept exploit and no evidence of in-the-wild exploitation at this time. The NVD SSVC assessment classifies exploitation as "none" and the attack as non-automatable, reflecting the high complexity required to mount a successful timing attack. The EPSS score is approximately 0.21%, placing it in the 12th percentile for exploitation likelihood within 30 days (GitHub Advisory). The CVE status is listed as "Deferred" and it is not currently listed in the CISA Known Exploited Vulnerabilities catalog.

The primary remediation is to upgrade the mirage-crypto-ec package to version 2.4.0 or later, which addresses the timing side-channel in NIST elliptic-curve scalar multiplication (GitHub Advisory). If immediate patching is not possible, consider isolating services using this library from untrusted network access to reduce the feasibility of timing measurements. Additionally, review applications using this library for exposure to timing attack scenarios and consider implementing additional side-channel protections or process isolation as interim measures.