CVE-2026-12860Network attack vector

Signature forgery via truncated NULL-less hash comparison

Published Aug 3, 2026 · Updated Aug 3, 2026

Improper RSA signature verification in Bouncy Castle Java before 1.85 allows remote attackers to bypass integrity checks with forged signatures. RSADigestSigner.verifySignature() compares only hash.length bytes after shifting offsets for a DigestInfo that omits NULL parameters, leaving the final two hash bytes unchecked. Bouncy Castle Java LTS before 2.73.12 is also affected; the default-enabled legacy path lowers second-preimage work by 16 bits across TLS, PKIX/CMS, and OpenPGP verification.

CVSS severity8.7
High
EPSS probability0.14%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper RSA signature verification in Bouncy Castle Java before 1.85 allows remote attackers to bypass integrity checks with forged signatures. RSADigestSigner.verifySignature() compares only hash.length bytes after shifting offsets for a DigestInfo that omits NULL parameters, leaving the final two hash bytes unchecked. Bouncy Castle Java LTS before 2.73.12 is also affected; the default-enabled legacy path lowers second-preimage work by 16 bits across TLS, PKIX/CMS, and OpenPGP verification.

The record

CVE
CVE-2026-12860
Published
Aug 3, 2026
Updated
Aug 3, 2026
Vendor
Legion of the Bouncy Castle Inc.
Product
Bouncy Castle Java
Classifications
CWE-347
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 3, 2026CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 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 <1.85

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Legion of the Bouncy Castle Inc. · Bouncy Castle Javaversion=0 <1.85
Legion of the Bouncy Castle Inc. · Bouncy Castle Java LTSversion=2.73.0 <2.73.12

Published CVSS scores

8.7Legion of the Bouncy Castle Inc.CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA: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.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-347Improper Verification of Cryptographic Signature

Public exploit references

No public exploit references are available in this record.

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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