8.7

CVE-2026-5500: Improper Validation of AES-GCM Authentication Tag Length in PKCS#7 Envelope Allows Authentication Bypass

Analyzed
AliasesUBUNTU-CVE-2026-5500DEBIAN-CVE-2026-5500ALPINE-CVE-2026-5500
Published 10-04-2026Last modified 10-04-2026

Vulnerability summary

CVE-2026-5500 is a high (CVSS 8.7) Improper Input Validation vulnerability in wolfssl. EPSS estimates a 0.48% chance of exploitation in the next 30 days, higher than 41.7% of scored vulnerabilities.

Priority
Prioritisesevere

Severe, CVSS 8.7 (CVE.org); no exploitation reported by the 5 checked sources; EPSS 0% (FIRST, 03-11-2026)

Source freshness unavailable

How is this decided?
CVSS score
8.7/10
010
High · v4.0 (CVE.org)
EPSS score
0.48%
0%100%
Low · +0.11 pp in 30 days
KEVNot listedNot listed by any tracked catalog.
RansomwareNot flaggedNo ransomware use recorded.
Public exploits0No public exploits recorded

Timeline

  1. 10-04-2026
    PublishedVulnerability first disclosed.
  2. 10-04-2026
    Last modifiedVulnerability information updated.

Description

wolfSSL's wc_PKCS7_DecodeAuthEnvelopedData() does not properly sanitize the AES-GCM authentication tag length received and has no lower bounds check. A man-in-the-middle can therefore truncate the mac field from 16 bytes to 1 byte, reducing the tag check from 2⁻¹²⁸ to 2⁻⁸.

CVSS metrics

7 scores · 5 sources · 2 versions

EPSS trend

Probability

0.48%

Chance of exploitation in the next 30 days

Percentile

42%

Versus all other CVEs

30-day change

Increase +0.11 pp

From 0.38% on 04-10-2026

04-10-202603-11-2026

Known exploited

Compare KEV catalogs
CISA KEV

Not in the CISA KEV catalog.

ENISA CNW

Not in the ENISA CNW catalog.

CIRCL

Not in the CIRCL catalog.

Public exploits

0 found

No public exploits indexed.

Weaknesses

CWE · root cause

Affected systems

Version check

Known conditions: network-reachable, no authentication, no user interaction (CVSS vector). Other conditions: not stated in public data.

Alpine1 product
  • wolfssl< 5.9.1-r0
Debian1 product
  • wolfsslAll versions (No fix recorded)
Ubuntu1 product
  • wolfsslAll versions (No fix recorded)
Wolfssl1 product

4 vendors · 4 products

References

5 links