CVE-2026-59640Network attack vector

Plaintext recovery via OpenPGP CFB error oracle

Published Aug 3, 2026 · Updated Aug 3, 2026

OpenPGP decryption in Bouncy Castle for Java before 1.85 allows remote attackers to recover plaintext via a CFB error oracle. PGPSymmetricKeyEncryptedData.getDataStream() checks two repeated IV bytes and throws PGPDataValidationException before MDC verification, exposing distinct failure outcomes. The same path affects Java LTS before 2.73.12 and FIPS bcpg-fips before 1.0.13, 2.0.13, and 2.1.13; exploitation requires adaptive chosen-ciphertext access to a decryption endpoint and yields two plaintext bytes per roughly 2^15 queries.

CVSS severity8.7
High
EPSS probability0.22%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

OpenPGP decryption in Bouncy Castle for Java before 1.85 allows remote attackers to recover plaintext via a CFB error oracle. PGPSymmetricKeyEncryptedData.getDataStream() checks two repeated IV bytes and throws PGPDataValidationException before MDC verification, exposing distinct failure outcomes. The same path affects Java LTS before 2.73.12 and FIPS bcpg-fips before 1.0.13, 2.0.13, and 2.1.13; exploitation requires adaptive chosen-ciphertext access to a decryption endpoint and yields two plaintext bytes per roughly 2^15 queries.

The record

CVE
CVE-2026-59640
Published
Aug 3, 2026
Updated
Aug 3, 2026
Vendor
Legion of the Bouncy Castle Inc.
Product
Bouncy Castle Java
Classifications
CWE-203
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 FIPSversion=1.0.0 <1.0.13; version=2.0.0 <2.0.13; version=2.1.0 <2.1.13
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:H/VI:N/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.

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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-203Observable Discrepancy

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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