GCM chunking can lead to bad tag exception on decryption

published 2026-05-08 6 mo ago modified 2026-10-26 13 d ago also GHSA-mx76-r943-rf8g , EUVD-2026-28534

cvss: 5.1; version 4.0, CNA
cisa kev: Not listed; not in CISA's catalog
epss: 0.2%; EPSS 0.2% chance of exploitation in 30 days, percentile 4%
public exploits: 0; none known

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.

Patch / fix

fixed in 3

maven org.bouncycastle:bcprov-lts8on 2.73.11
Legion of the Bouncy Castle Inc. BC-LTS 2.73.11
Legion of the Bouncy Castle Inc. BC-FJA 2.1.3

CISA SSVC

Exploitation: none
Automatable: no
Technical impact: partial
Assessed: 6 mo ago (2026-05-08)

Exploit prediction

0.16% chance of exploitation in the next 30 days, higher than 4% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by	version	score	vector
CNA	4.0	5.1	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/S:N/RE:M/U:Amber
CNA	4.0	5.1	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

Affected packages

ecosystem	package	affected	fixed in
maven	org.bouncycastle:bcprov-lts8on	>=2.73.0, <2.73.11	2.73.11

Affected products

Legion of the Bouncy Castle Inc. BC-LTS
Legion of the Bouncy Castle Inc. BC-FJA

Classification

Weakness

CWE-1068 Inconsistency Between Implementation and Documented Design
CWE-354 Improper Validation of Integrity Check Value

References

github.com /bcgit/bc-java/wiki/CVE%E2%80%902026%E2%80%908149
vendor-advisory, web
nvd.nist.gov /vuln/detail/CVE-2026-8149
advisory

Sources

CVE List CVE-2026-8149
GitHub Advisory GHSA-mx76-r943-rf8g
NVD CVE-2026-8149

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

Summary