Medium

CVE-2026-8149 — GCM chunking can lead to bad tag exception on decryption

A vulnerability in Legion of the Bouncy Castle Inc. BC-LTS bcprov-lts8on on X86_64, AVX, AVX-512f, Linux, Legion of the Bouncy Castle Inc. BC-FJA bc-fips on Linux, X86_64, AVX, AVX-512f. This vulnerability is associated with program files gcm128w, gcm512w, gcm128w.C, gcm512w.C. This issue affects BC-LTS: from 2.73.0 before 2.73.11; BC-FJA: from 2.1.0 before 2.1.3.

Published May 8, 2026 · Updated Oct 13, 2026 · Sources: NIST National Vulnerability Database, CVE Program (cve.org) e CISA ADP · CNA: bcorg

Low

Who exploits it and how urgent it is

A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.

No exploitation signal in the sources consulted so far.

How the score was calculated

EPSS 0.2% (30-day exploitation probability)+1
Technical severity (medium)+3

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.

Exploitation

Not confirmed

Not in CISA KEV — an absence of record, not proof it is unexploited.

EPSS FIRST

0.17%

ahead of 6% of scored CVEs · Oct 14, 2026

Affects

Legion of the Bouncy Castle Inc.

BC-FJA and 1 more

CVSS base

5.1

Medium · 2 source(s)

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.

Exploitation

None

none · proof-of-concept · active

Automatable

can an attacker script the kill-chain steps

Technical impact

Partial

partial · total control of the vulnerable component

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-LTS).
No fix documented in the sources: reduce exposure and monitor the vendor advisory.
Search available logs for exploit probes, 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	≥ 2.1.0 and < 2.1.3	Vulnerable	CVE Program (cve.org) e CISA ADP
Legion of the Bouncy Castle Inc.	BC-LTS	≥ 2.73.0 and < 2.73.11	Vulnerable	CVE Program (cve.org) e CISA ADP

Attack characteristics

The CVSS vector, decoded. It describes the attack, not your exposure to it.

Attack vector

Local

Attack complexity

Low

Attack requirements

None

Privileges required

None

User interaction

None

Scope

Confidentiality (vulnerable system)

None

Integrity (vulnerable system)

None

Availability (vulnerable system)

Low

Confidentiality (subsequent)

None

Integrity (subsequent)

None

Availability (subsequent)

None

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
5.1	CVSS 4.0	Medium	—	—	91579145-5d7b-4cc5-b925-a0262ff19630 via NIST National Vulnerability Database
5.1	CVSS 4.0	Medium	—	—	bcorg via CVE Program (cve.org) e CISA ADP

CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/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:N/AU:X/R:X/V:X/RE:M/U:Amber

(score shown at the top: 91579145-5d7b-4cc5-b925-a0262ff19630)

Weakness MITRE

Weakness class according to MITRE’s CWE catalog.

CWE-1068

Other CVEs with this weakness →

EPSS over time FIRST

Oct 13, 2026 → Oct 14, 2026 · 2 reading(s) · max 0.17%

Detection

Read off the CVSS vector and the weakness class. Starting points, not tested rules.

Local/physical vector: focus on endpoint telemetry (EDR) from affected hosts.

endpoint telemetry (EDR)

Timeline

What happened to this CVE, newest first.

2026
Affected products added · legion of the bouncy castle inc./bc-lts, legion of the bouncy castle inc./bc-fja
Oct 13, 2026 · CVE Program (cve.org) e CISA ADP
SSVC assessment updated
Oct 13, 2026 · CVE Program (cve.org) e CISA ADP
Record published
Oct 13, 2026
CVSS changed · 5.1
Oct 13, 2026 · NIST National Vulnerability Database
Source status changed · → Awaiting Analysis
Oct 13, 2026 · NIST National Vulnerability Database
Record created in this database
Oct 13, 2026 · NIST National Vulnerability Database
CVE published
May 8, 2026 · bcorg

Source activity

Repeated readings are counted rather than listed.

1× Official description updated · Oct 13, 2026 – Oct 13, 2026

References

1 on the record

github.com/bcgit/bc-java/wiki/CVE%E2%80%902026%E2%80%908149
vendor-advisory, NIST National Vulnerability Database

Elsewhere on this site

Legion of the Bouncy Castle Inc.
every CVE for this vendor

CWE-1068
other pages naming this weakness

Related CVEs (same products)

High CVE-2026-85515 OpenPGP message truncation not reported, bypassing the SEIPDv1 integrity check 12d
High CVE-2026-71888 CMS AuthenticatedData exposes attacker-inserted authAttrs when digestAlgorithm is absent 12d
Medium CVE-2026-71892 CMS key-transport recipient key-size validation never runs for RFC 9709 HKDF-derived keys 12d
High CVE-2026-71889 PKIXCertPathReviewer does not apply X.509 name constraints to the target certificate 12d
Low CVE-2026-15997 Native ARM SHA3 / SHAKE `restoreFullState` fails to detect size_t underflow in a crafted encoded state Jul 16, 2026

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-2026-8149 is "GCM chunking can lead to bad tag exception on decryption", rated Medium. 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 5.1 describes technical severity. EPSS 0.17% 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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