CVE-2026-87733Public exploit

ECDSA signature forgery via infinity-point public key

Published Sep 9, 2026 · Updated Sep 9, 2026

Improper ECDSA public-key validation in OCaml mirage-crypto-ec before 2.2.0 allows local users to forge signatures without a private key. The P256, P384, and P521 Dsa.pub_of_octets functions accept the 0x00 SEC1 infinity encoding without rejecting the non-finite point. Exploitation requires an application to accept attacker-controlled public-key bytes and rely on the resulting key for ECDSA verification.

CVSS severity6.2
Medium
EPSS probability0.10%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper ECDSA public-key validation in OCaml mirage-crypto-ec before 2.2.0 allows local users to forge signatures without a private key. The P256, P384, and P521 Dsa.pub_of_octets functions accept the 0x00 SEC1 infinity encoding without rejecting the non-finite point. Exploitation requires an application to accept attacker-controlled public-key bytes and rely on the resulting key for ECDSA verification.

The record

CVE
CVE-2026-87733
Published
Sep 9, 2026
Updated
Sep 9, 2026
Vendor
OCaml
Product
mirage-crypto-ec
Classifications
CWE-295, T1553
Attack vector
local
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 9, 2026CVE publishedPublication date reported by the CVE source.
  2. Sep 9, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=0 <2.2.0

What conditions does exploitation require?

Attack vectorlocal
Required privilegesunauthenticated

What is affected?

OCaml · mirage-crypto-ecversion=0 <2.2.0

Published CVSS scores

6.2OCaml Security AdvisoriesCVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-295Improper Certificate Validation
T1553Subvert Trust Controls

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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