CVE-2026-85515 — OpenPGP message truncation not reported, bypassing the SEIPDv1 integrity check
In Bouncy Castle for Java before 1.86, a truncated OpenPGP encrypted message was accepted with no error reported, and on the SEIPD version 1 path with no integrity check performed at all. RFC 9580 sec. 13.7 permits an implementation to release the cleartext of the fully authenticated chunks when streaming but requires it to indicate a clear error as soon as the truncation is detected, and to report suspect integrity when it discovers malleable ciphertext. The truncation was detected and then discarded: when a message is truncated but the length field of the enclosing packet is left unchanged, BCPGInputStream.PartialInputStream raises an EOFException for the missing ciphertext, and BCPGInputStream.nextPacketTag() reports an EOFException as a clean end of message, so the packet stream above it stopped as though no packets remained. On the AEAD path (SEIPD version 2 and the version 5 AEAD packet), when the literal data packet ended on an AEAD chunk boundary and the consumer read in increments smaller than one chunk, the look-ahead for the packet after the literal triggered the truncated chunk read, so BcAEADUtil and JceAEADUtil never reached the trailing message tag of sec. 5.13.2 that authenticates the total plaintext length; the caller received the plaintext of the fully authenticated chunks, every packet following the literal was silently dropped, and no exception was raised, so a signed and encrypted message read back as a well-formed unsigned one. Every byte released on that path remained individually authenticated, making this a missing truncation error rather than a forgery, and it is a residual of CVE-2026-12817, which closed the same outcome for an attacker who corrects the outer packet length. On the SEIPD version 1 path the consequence was more serious: IntegrityProtectedInputStream verifies the modification detection code from close(), and reached close() only by closing itself when a read of it returned -1, which a truncated message never produces, so PGPEncryptedData.verify() never ran and the recipient was handed CFB-decrypted plaintext on which no integrity check of any kind had been performed. Measured on a message truncated into that shape, 136 distinct single-byte modifications of the ciphertext produced accepted, altered plaintext with no exception raised. Reachability is a property of the message rather than of attacker-supplied input: the AEAD shape held for 3 of 131 consecutive payload lengths measured, and the SEIPD version 1 shape for one payload length in sixteen, at a truncation offset that did not move with the payload length. The low-level API is unaffected, a caller that invokes PGPEncryptedData.verify() directly getting the check regardless, as are consumers reading in increments of a whole AEAD chunk or more. The AEAD decryption streams now re-throw such an EOFException as a plain IOException, which nextPacketTag() does not launder; OpenPGPMessageInputStream.close() now closes its layer's integrity-protected stream itself rather than relying on that stream having seen the end of its data; and IntegrityProtectedInputStream.close() was made idempotent, as java.io.Closeable requires, which that depends on, since the stream is genuinely closed twice on the ordinary path and PGPEncryptedData.verify() consumes the digest state behind it and cannot be run a second time. This issue also affects Bouncy Castle for Java LTS before 2.73.13, on the AEAD route only, as that edition does not ship the high-level OpenPGP API the SEIPDv1 route runs through. It also affects Bouncy Castle for Java FIPS (BC-FJA) before bcpg-fips 1.0.14 (1.0.X series), 2.0.14.1 (2.0.X series) and 2.1.14 (2.1.X series), on the AEAD route only, as those editions do not ship the high-level OpenPGP API.
Who exploits it and how urgent it is
A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.
How the score was calculated
- EPSS 0.2% (30-day exploitation probability)+1
- Technical severity (high)+6
The score orders the patch queue; it does not replace your asset context (internet exposure, criticality, compensating controls).
Triage
Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.
CISA SSVC assessment CISA
Three decision points CISA publishes for the CVEs it assesses (SSVC 2.0.3). A stakeholder decision, not a severity score.
Remediation
Fixes and mitigations documented by the sources — linked to the original advisory.
No fix documented by the sources we poll. That does not mean none exists: check the vendor advisory.
First 24 hours
Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.
- Identify exposed assets running the affected vendor/product/version combinations (Legion of the Bouncy Castle Inc. BC-FJA, Legion of the Bouncy Castle Inc. BC-JAVA, Legion of the Bouncy Castle Inc. BC-LTS-JAVA).
- The attack is network-based and needs no privileges: restrict exposure (ACLs, VPN, WAF) until patched.
- No fix documented in the sources: reduce exposure and monitor the vendor advisory.
- Search available logs for exploit probes matching the vulnerability class (integrity), errors and authentication anomalies.
Affected scope
Vendor, product and versions as the sources word them.
| Vendor | Product | Versions | Status | Source |
|---|---|---|---|---|
| Legion of the Bouncy Castle Inc. | BC-FJA | ≥ 1.0.7 and < 1.0.14≥ 2.0.7 and < 2.0.14.1≥ 2.1.0 and < 2.1.14 | Vulnerable | CVE Program (cve.org) e CISA ADP |
| Legion of the Bouncy Castle Inc. | BC-JAVA | ≥ 1.74 and < 1.86 | Vulnerable | CVE Program (cve.org) e CISA ADP |
| Legion of the Bouncy Castle Inc. | BC-LTS-JAVA | ≥ 2.73.0 and < 2.73.13 | Vulnerable | CVE Program (cve.org) e CISA ADP |
Attack characteristics
The CVSS vector, decoded. It describes the attack, not your exposure to it.
Every base score collected
Sources score independently and may disagree; each row says who scored it and under which version.
| Score | Version | Severity | Expl. | Impact | Scored by |
|---|---|---|---|---|---|
| 8.2 | CVSS 4.0 | High | — | — | 91579145-5d7b-4cc5-b925-a0262ff19630 via NIST National Vulnerability Database |
| 8.2 | CVSS 4.0 | High | — | — | bcorg via CVE Program (cve.org) e CISA ADP |
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/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 (score shown at the top: 91579145-5d7b-4cc5-b925-a0262ff19630) Weakness MITRE
Weakness class according to MITRE’s CWE catalog.
EPSS over time FIRST
Oct 13, 2026 → Oct 14, 2026 · 2 reading(s) · max 0.16%
Detection
Read off the CVSS vector and the weakness class. Starting points, not tested rules.
- Prioritize edge telemetry for the network-reachable component (proxy, WAF, IDS/IPS).
Timeline
What happened to this CVE, newest first.
- 2026
- Affected products added · legion of the bouncy castle inc./bc-java, legion of the bouncy castle inc./bc-lts-java, legion of the bouncy castle inc.
- SSVC assessment updated
- Record published
- CVSS changed · 8.2
- Source status changed · → Awaiting Analysis
- Record created in this database
- CVE published
Source activity
Repeated readings are counted rather than listed.
- 1× Official description updated · Oct 13, 2026 – Oct 13, 2026
References
2 on the record
Elsewhere on this site
Related CVEs (same products)
- High CVE-2026-71884 Packet CTR reports a full success length after the counter is exhausted 6d
- Medium CVE-2026-97873 Legacy PBES1 and PKCS#12 PBE iteration count honoured unbounded in the raw JCA provider 12d
- High CVE-2026-71891 BLS12-381 key validation accepts a public key built on a foreign curve 12d
- High CVE-2026-71889 PKIXCertPathReviewer does not apply X.509 name constraints to the target certificate 12d
- Medium CVE-2026-71892 CMS key-transport recipient key-size validation never runs for RFC 9709 HKDF-derived keys 12d
- High CVE-2026-71890 MLS external commit can remove an arbitrary group member 12d
Not in any source we poll
Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.
- No fixed version, patch or mitigation documented.
- No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
- No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
- No exploit packet captures, log samples, or incident case IDs supplied.
Answered from this record
Text assembled only from the fields above — no additional claims.
What should defenders know first?
CVE-2026-85515 is "OpenPGP message truncation not reported, bypassing the SEIPDv1 integrity check", rated High. It affects BC-FJA (Legion of the Bouncy Castle Inc.); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. CVSS 8.2 describes technical severity. EPSS 0.16% estimates the probability of exploitation in 30 days; neither replaces your asset context. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.
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