CVE catalog

CVE-2026-71891

In Bouncy Castle for Java before 1.86…

In Bouncy Castle for Java before 1.86, BLS12_381BasicScheme.keyValidate, and so BLSPublicKeyParameters and every BasicScheme, MessageAugmentation and ProofOfPossession verify and aggregateVerify that gate on it, accepted a public key built on a foreign ECCurve that merely shares BLS12-381's field characteristic. The prime-order subgroup check trusts a point's own curve to name its cofactor, since ECPoint.satisfiesOrder returns true outright when the curve's cofactor is one, so a point on a curve with a different equation and a cofactor forged to one passed keyValidate despite not being a G1 point at all. In BC's pairing implementation such a point contributes the identity in the target group, so an aggregate signature verified against a set of public keys including it is accepted even though it contains no signature for that key and message pair, admitting a phantom signer. keyValidate now first confirms that the point's curve carries exactly the canonical G1 field, equation, order and cofactor before any subgroup check. The issue is reachable only where an application constructs an ECPoint on an explicit, non-canonical curve and accepts it as an authority-bearing key; the standard 48-byte compressed-point decoder always supplies the canonical curve and was never affected.

Severity: High · CVSS 7.1CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:Amber
Published: Oct 3, 2026, 8:56:01 AM UTC
Updated: Oct 3, 2026, 9:17:05 AM UTC
Source: [NVD] · [CVE record]
EPSS: 0.17% · Oct 27, 2026

Projects and upstream resources

[bouncycastle][Source-reported homepage]

Reported versions and fixes

Each observation applies to its named package, distribution, and release. Distribution backports can fix a vulnerability while retaining an older upstream version number.

Version impact has not been established. The original provider fields are retained below.

Provider details and historical evidence

Original provider fields

{
  "package_releases": [
    {
      "name": "bouncycastle",
      "status": "fixed",
      "release": "sid",
      "version": "1.86.2-1"
    },
    {
      "name": "bouncycastle",
      "status": "fixed",
      "release": "forky",
      "version": "1.86-1"
    },
    {
      "name": "bouncycastle",
      "status": "vulnerable",
      "release": "trixie",
      "version": "1.80-3"
    },
    {
      "name": "bouncycastle",
      "status": "vulnerable",
      "release": "bookworm",
      "version": "1.72-2"
    }
  ],
  "fixed_versions": [
    {
      "bug": null,
      "name": "bouncycastle",
      "type": "source",
      "origin": null,
      "release": "sid",
      "urgency": "not yet assigned",
      "fixed_version": "1.86-1"
    },
    {
      "bug": null,
      "name": "bouncycastle",
      "type": "source",
      "origin": null,
      "release": "forky",
      "urgency": "not yet assigned",
      "fixed_version": "1.86-1"
    },
    {
      "bug": null,
      "name": "bouncycastle",
      "type": "source",
      "origin": null,
      "release": "trixie",
      "urgency": "not yet assigned",
      "fixed_version": ""
    },
    {
      "bug": null,
      "name": "bouncycastle",
      "type": "source",
      "origin": null,
      "release": "bookworm",
      "urgency": "not yet assigned",
      "fixed_version": ""
    }
  ],
  "distribution_packages": []
}

OpenFactory catalog packages

Matching against OpenFactory catalog package versions is in progress.

[Debian 12 (Bookworm)]

[libbcjmail-java]Unknown
Source package: [bouncycastle]
Details (2)
- 1.72-2 · all · bookworm
  Affected
  nvd · bouncycastle · debian · bookworm; nvd · bouncycastle · debian · 12
- 1.72-2 · all · bookworm
  Affected
  nvd · bouncycastle · debian · bookworm; nvd · bouncycastle · debian · 12
[libbcmail-java]Unknown
Source package: [bouncycastle]
Details (2)
- 1.72-2 · all · bookworm
  Affected
  nvd · bouncycastle · debian · bookworm; nvd · bouncycastle · debian · 12
- 1.72-2 · all · bookworm
  Affected
  nvd · bouncycastle · debian · bookworm; nvd · bouncycastle · debian · 12
[libbcpg-java]Unknown
Source package: [bouncycastle]
Details (2)
- 1.72-2 · all · bookworm
  Affected
  nvd · bouncycastle · debian · bookworm; nvd · bouncycastle · debian · 12
- 1.72-2 · all · bookworm
  Affected
  nvd · bouncycastle · debian · bookworm; nvd · bouncycastle · debian · 12
[libbcpkix-java]Unknown
Source package: [bouncycastle]
Details (2)
- 1.72-2 · all · bookworm
  Affected
  nvd · bouncycastle · debian · bookworm; nvd · bouncycastle · debian · 12
- 1.72-2 · all · bookworm
  Affected
  nvd · bouncycastle · debian · bookworm; nvd · bouncycastle · debian · 12
[libbcprov-java]Unknown
Source package: [bouncycastle]
Details (2)
- 1.72-2 · all · bookworm
  Affected
  nvd · bouncycastle · debian · bookworm; nvd · bouncycastle · debian · 12
- 1.72-2 · all · bookworm
  Affected
  nvd · bouncycastle · debian · bookworm; nvd · bouncycastle · debian · 12
[libbctls-java]Unknown
Source package: [bouncycastle]
Details (2)
- 1.72-2 · all · bookworm
  Affected
  nvd · bouncycastle · debian · bookworm; nvd · bouncycastle · debian · 12
- 1.72-2 · all · bookworm
  Affected
  nvd · bouncycastle · debian · bookworm; nvd · bouncycastle · debian · 12
[libbcutil-java]Unknown
Source package: [bouncycastle]
Details (2)
- 1.72-2 · all · bookworm
  Affected
  nvd · bouncycastle · debian · bookworm; nvd · bouncycastle · debian · 12
- 1.72-2 · all · bookworm
  Affected
  nvd · bouncycastle · debian · bookworm; nvd · bouncycastle · debian · 12

[Debian 13 (Trixie)]

[libbcjmail-java]Unknown
Source package: [bouncycastle]
Details (2)
- 1.80-3 · all · trixie
  Affected
  nvd · bouncycastle · debian · 13
- 1.80-3 · all · trixie
  Affected
  nvd · bouncycastle · debian · 13
[libbcmail-java]Unknown
Source package: [bouncycastle]
Details (2)
- 1.80-3 · all · trixie
  Affected
  nvd · bouncycastle · debian · 13
- 1.80-3 · all · trixie
  Affected
  nvd · bouncycastle · debian · 13
[libbcpg-java]Unknown
Source package: [bouncycastle]
Details (2)
- 1.80-3 · all · trixie
  Affected
  nvd · bouncycastle · debian · 13
- 1.80-3 · all · trixie
  Affected
  nvd · bouncycastle · debian · 13
[libbcpkix-java]Unknown
Source package: [bouncycastle]
Details (2)
- 1.80-3 · all · trixie
  Affected
  nvd · bouncycastle · debian · 13
- 1.80-3 · all · trixie
  Affected
  nvd · bouncycastle · debian · 13
[libbcprov-java]Unknown
Source package: [bouncycastle]
Details (2)
- 1.80-3 · all · trixie
  Affected
  nvd · bouncycastle · debian · 13
- 1.80-3 · all · trixie
  Affected
  nvd · bouncycastle · debian · 13
[libbctls-java]Unknown
Source package: [bouncycastle]
Details (2)
- 1.80-3 · all · trixie
  Affected
  nvd · bouncycastle · debian · 13
- 1.80-3 · all · trixie
  Affected
  nvd · bouncycastle · debian · 13
[libbcutil-java]Unknown
Source package: [bouncycastle]
Details (2)
- 1.80-3 · all · trixie
  Affected
  nvd · bouncycastle · debian · 13
- 1.80-3 · all · trixie
  Affected
  nvd · bouncycastle · debian · 13

Observed: Oct 23, 2026, 7:46:37 PM UTC

References

[CERT-Bund public advisories] · [Debian Security Tracker] · [FIRST EPSS] · [National Vulnerability Database (NVD)] · [OSV Package Vulnerability Database] · [Red Hat security advisories and VEX] · [SUSE security advisories and VEX]